, having had to replace the original - would it make any difference to switch the fuel at the pressure gauge? I.e., I'm not using the pressure gauge anyway for cruise settings, sow what good would it do to switch them? Or am I missing something in your suggestion?
BTW, regarding Ernie's comments, I also ran the tanks dry, switch to the aux. tanks, then landed and refueled. Then a few days later I had them top off the tanks to be sure they were both full, and reading the fuel truck's meter in both circumstances it appeared that the tanks were holding their nominal 92 gals. THEN I did my flight testing, and whichever engine was set on the tanks in question ran out sooner than the other - by 30 mins. and 22 mins. respectively.
10 min.s or so I could accept between engines as accounted for by wear, age, lack of total accuracy in gauge settings, etc. But 20 and 30 mins. seems to me more than I should be living with.
Gmas replied
Oh… I thought you were using the fuel flow gauges for the flow setting… if you are using the EGT.. and its new… did they calibrate it… after they put it in… EGTs are kinda funny about being accurate… but, they are somewhat reliable to do the job… but, you need to have them use the test box on it to set it up… you can do the same thing if you take the probe out of the engine… (if its stock).. and using a source that is kept the same… test each and adjust the meter to match… It works much better if you use the alcor test set.. and then use the eutectic indicator to make sure it is within range... I have seen a shop use a brenzomatic torch… but, they took the soldering tip.. which was copper and drilled a cross hole in it… for the probe tip… then when they lit it off… it would make the tip get hot… and glow red… about 900 deg or so… was registered… on the temp probe.. that was attached.. and plugged into a fluke meter… From that they then set the meter inside… for the bottom of the scale… then they turned up the heat.. and got a reading of 1500… and set the meter for the top of the scale… and called it good… but, without the necessary equipment… you don't stand a chance… yes the egt is a relative indicator… don't go by the numbers.. or tick marks… for peak… you are looking for the needle to quit going up… and then we back it down a certain amount… it is not the calibrated number that is indicated and thus the reason Alco didn't put numbers on the gauge….
Several other things can be factors too… one is that the probe is not put into the same place on each engine… and even thought Cessna tried to make them uniform in location… they are not drilled that accurate… another is the dia of the pipe… and the restrictions to the exhaust gases… the back having a muffler… will indicate a hotter temp… while the fwd one goes right out the muff.. and so no back pressure to keep the heat… (just when you thought everything was the same…) lots of variables that one has to take into account… so what is the answer… well at each power setting (Mp/RPM) and altitude the EGT is going to read different…. Even with the different Rh in the air… or temp… the best way to check for a inaccurate gauge is to…. Do it the old way… lean to quit.. and then set one mark down… or 1/8 inch forward… but, that is kinda crude… it is best to have the guage checked again… after being broke in…(yess EGT gauges and probes will move around… for the first couple of hours) and then test it again.. as each time you do.. it will get more accurate and equal… but, that takes into consideration that the lead length and connections are all the same….
So you can forget the fuel flow guage… if your not setting it by that.. and go to the EGT for a accuracy check… by artificial simulated means… then you can see how far off each engine is… most shops will tweek them … even though the engines burn different… to match in flight… something about pilots like seeing both needles at the same point on the gauge… regardless of if they are in reality…
But, I thought you said that the fuel capacity was what you were after…. And that the original question was how come I can only get so much into each side…or tank
Paul Sharp replied
Yes, the fuel capacity is what I'm after - or whatever makes it "seem" less on the front tank v. the rear one. If that's a matter of engine temp, then it seems that there's quite a discrepancy. At least to me, a half-hour is a fair discrepancy!
So I'm not sure why the front engine quits 1/2 hour before the rear when both tanks fill up with right close to 92 gals. And when I cross-feed them then the rear engine quits 22 mins. before the front. So I think that shows that the running temps probably are about the normal for discrepancy. But where's the darn fuel disappearing to?
If it's not coming out of the tank, then my mechanics can't find it. They took the covers off and inspected the inside of the tank. It seemed all OK and the rear outlet as well as the front seemed fine. They drained fuel throug the outlets and it came out fine, etc.
Boy, I'm sure stumped on this one.
Ernie Martin replied
I think you can ignore the data you gather when cross-feeding, because in cross-feeding the fuel/vapor return (which is roughly equal to the actual fuel consumed by the engine) goes to the tank feeding the OTHER engine. The test without cross-feeding yields valid data which suggests your front engine IS using more fuel. But half an hour is only about 10% difference in consumption! Run through the numbers. If the front uses 10 gal/min and the back uses 9 gal/min, 46 gal will last 4.6 hours for the front and 5.1 hours for the back. If your front engine runs hotter, that explains the 10%. I have virtually the same half-hour difference difference because of temperature, but backwards -- it's my rear engine which runs hot.
Paul Sharp then replied
That's really an interesting point about the cross-feeding. Let me run a sample at that to see if I'm getting your point. Suppose I start out with 10 gals. in each tank. I run long enough to burn 5 gals. total through the front engine, which means say 5 gals also gets returned from the fuel-vapor line. That leaves 5 gals. in that tank. Meanwhile the rear only burns say 3 gals. A similar 3 are returned, so the rear tank should have 7 gals left. If the front is running hotter, then all that seems to make sense. NOW if I cross-feed under the same time and settings what I get is the front tank sending 3 to the rear engine, but gets 5 back from the other tank which sends 5 to the front engine and gets only 3 back from the opposite tank. So the front tank should end up with 7 gals. and the rear with only 3 gals. Since the rear tanks is feeding the front engine then it should stop sooner than ever, shouldn't it? But in my case the rear engine, during cross-feeding, stopped 22 mins. sooner than the front engine (v. the 30 or so mins. sooner the front engine quits when NOT cross-feeding). ??? Do I have that right?
And I nearly always run at 74% power, so am using about 23-24 GPH. That would only make the percentage go a little higher, or course, but it does seem strange to me to be that far off. Since others are reporting something similar, maybe it makes sense though. My front engine was rebuilt about 200 hrs. ago, and the rear is nearing the latter part of the normal TBO cycle. (Seems to me that the rear should then run hotter than the front, although maybe that's just a misconception on my part or perhaps just the way my two engines tend to shake out.)
Ernie MArtin the replied
I don't think cross-feeding works like your example. I'll tell you what I think and maybe GMAs will jump right in and settle it. Suppose we use your same example. Suppose you start out with 10 gals. in each tank. I run long enough to burn 5 gals. total through the front engine, which means 10 gal flowed to the front engine and 5 gals returned from the fuel-vapor line. That leaves 5 gals in that tank. Meanwhile the rear only burns say 3 gals. But here is the difference: 10 gals (not 6) flowed to the rear engine and 7 are returned, so the rear tank should have 7 gals left. If the front is running hotter, then all that seems to make sense. NOW if you cross-feed under the same time and settings what you get is the left/front tank sending 10 to the rear engine (3 of which are consumed and 7 are returned to the right/rear tank), but that left/front tank gets 5 back from the front engine (which was fed from the right/rear tank), leaving the left/front tank with 5 gals. The right/rear tank, which fed 10 gals to the front engine, gets 7 back from the rear engine. So at the end of this period, the left/front tank (cross-feeding the rear engine) has 5 gals, and the right/rear tank (cross-feeding the front engine) has 7 gals. Therefore, the rear engine, during cross-feeding, should indeed stop before the front engine, even though it's the front engine which has the higher consumption. In short, cross-feeding adds considerable complexity to the fuel flow and makes it virtually impossible to figure out what's happenning.
Your front engine, overhauled recently, SHOULD run cooler than the rear one, unless it's still tight, so it's hard to explain why the front engine is exhibiting greater consumption. What do the guages -- head temp and oil temp -- say?
Hope this helps.
Jim Rainer then added
I may be missing something and you may be losing fuel but I apporach this a little differently. First, mine is a G model with 148 gallon integral tanks - I don't run them dry.
After nearly every flight, I check the fuel consumption between the engines just to keep up. My rear burns more (it's 100 hr SMOH and front is 600 SMOH and rear runs slightly hotter.)
The key to accurately determine the difference is to always be sure the tanks are full on take off. This means being on level ground (not one wing lower than other) and fill each tank twice.
What I am doing is checking consumption between engines - not fuel capacity. My mechanic says the only way to check fuel capacity is to completely empty the tanks and refill. This is a process we are currently going through to calibrate my fuel guages.
To which Paul Sharp replied
Since I can run mine dry, I can then top them off - and I do it twice, too, since it takes a little time to settle, and I do it on level ground - and I can use the fuel truck readings to see that they both take really close to the advertised 92 gals.
And when I've run these tests, I've started with full tanks and run them dry, so I'm getting as accurate a "quantity" burned measurement as I can figure. I simply switch to the aux. tank when the front quits and continue running the rear until it quits before switching it to the aux. tank and I can see just how long the diff. is in minutes.
Gmas then added
Well.... if its not leaking then its either got to be bruning it or its getting sucked out of the tanks... You did not mention if you had the older gas caps or the new ones... also... what about the vents... and the check valves that are in them... are they open and leaking fuel out... sometimes people fly with one wing down... why I haven't figured out yet but they have the airplane trimed that way... and it causes some of the top fuel to leak out through the vent... One way to check this is to go fly for an hour... and full the tanks again... and accruatly measur the fuel... then go fly for 2 hrous... and see how much more different the fuel useage is...
While it is true that the fuel returns to the proper tank that the pump is hard lined to... your report shows that if you xfeed the opposite engine is runing out of fuel at about the same time.... and while it is true the if the returned fuel is less because the hard lined engine is burning it... causing the xfeed engine to run out first... it is more likely that you would see the differance on the fuel pressure guage... only if both systems are set up the same...
Now if no leaks or anything other can be determined as the reasion that the fuel time is less... then its got to be the engine hp or temp... and the fact that we know from your report that the fwd engine is runing out of fuel first... then it has to be burning more... by either more hp or richer mixture... which again leads us back to instrument calibration...
Most of the time because the two engines are at differnt elevations... the rear engine is set by the pilot to actually run leaner... because it has the fuel head pressure... the reasion why... its higher than the fwd engine which is lower... when the two systems are set the same... on the bench but, you will find that the rear spider (fuel distrubitor) has a different spring pressurre for the cutoff... because of this... To calibrate the two systems most of the time the tech does not take into account the fuel head pressure and when adjusting the rear engine the test set is at a lower elevation... it reads about 1/2 lb of fuel pressure with the engin off... where as the fwd engine is about 0... This is why when we adjust the engines it... is advisable to keep the pressure test system... at the level of the pump... on the engine...
So where does it leave the mechanic... well he has looked in the tanks and has checked all the attachments... and we have checked for flow... and it seems that the problem is on the left wing.. or the fwd engine.. or its instrumentation.. which supports it... which is making the pilot have different readings and settings... you have tried to match the engines as close as you can to the power and fuel settings... by using the EGT and MP ... and when the tanks were xfed... the opposite engine stoped about the same time ... and flying wing low would cause a difference in the fuelage that goes back into the tank.... unless its going out the vent.. or filler...
So that only leaves the vents and the engine...
Now if its was the vents you would be able to tell by the 1 hour and 3 hour test... because at 1 hour you would loose more than at the 3 hour mark if it is the same.. then we go look at the instrumentation and engine for that side...
Now to see if it is the engine.. then a simple flight of reduced power on the higher flow engine... less hp less fuel flow... or.... you can do a flow check... as well as check the mags for proper timing... compression testing ... balanced... remember we are only dealing with 15-20 %... or as one of the others have said about 1/2 gallon per hour... but, with enough time and money you can and should be able to balance the engines...
Gmas then added
Well did you solve the riddle yet... yes if you crossfeed the engines the clue stands out... (take a pencil and paper and draw out the fuel system... and just use a 3 gal return figure... and suppose both engines are burning equal, then one twice as much... and then crossfeed... figure time and fuel flow for 9 gal/hr if the engine is working ok... and 13 for the one that is not..... make up a table and calculate it out... ) and one of you above has gotten on the right track but, exited left... when you said that the rear will always go first... The clue is that if the return from the pump.. which is an orfice and fixed... is returning 3 gallons per hour... back to the tank for each engine...(basicly) now if you... have each return to the opposite tank... and one engine is burning more than the other... the opposite engine will run out of gas even faster than when each engine is on their assigned tanks... clue... so if the fwd engine is runing and burning more fuel than the rear and you crossfeed... then the rear will run out of fuel faster than... the original 30 min... so we can determine if the engines are burning more... now if it were the wing tank getting sucked dry from a cap leaking.. or vent ... what would we have... Hmmmmm.... you guys are getting better at the dective game... but, we have one more step.. on the mans situation.. now how to solve it... what steps and test can we do... and no you can't go look at the filler caps and vents... lets do this theroritical situation analysis...
Fuel injection System
Gmas put the following message on the message board
A pilot came into the shop the other day and was complaining about the fact that his EGT was not working right... WE then put the test set on the indicator and probes and found that it was in fact working correctly but found another problem instead... His fuel flow was off... The on board pressure guage was not going to red line when full power was being applied. Showing that his fuel flow was off... when questioned he said that this happens ever year when it gets hot... and said that it must be the fuel thinning out as it get warmer.... Hmmm... how many of you believe this... I hope not many. The IO-360/TISO engines used in the mixmasters have a simple fuel system... but, sometimes the mechanics are horrified to touch or adjust them. IT IS THE CLUBS RECOMENDATION AS WELL AS CONT ENG. THAT THE FUEL SYSTEM BE CHECKED AT LEAST TWICE A YEAR WHEN THE SEASIONS CHANGE During this check a CALIBRATED test set (means expensive) is used to make sure that the system is working correctly. Now most mechanics use the unmetered fuel pressure to adjust the system... which is the cause of our pilots problem here We have found that this only gives you half of the picture of how your fuel system is working... and in this case even the fuel flow guage was out of calibration... (things get old and need adjustment) The correct proceedure is to monitor the un-metered as well as metered fuel pressures... along with the typical fuel flows... all monitored by a calibrated test set. In our pilots case... he was actually runing the engine on the lean side of the curve and the EGT would not peek at the proper temp... until he got to altitude.. which nat takes less fuel. This resulted in a compression and boreschope check of his cyc on the engines to make sure that he did not burn the valves because of this condition. The result of this story is .... make sure you get your check up at least twice a year when the seasons change....its cheep takes less than an hour and it could save you some bucks if not your butt... Our pilot has other problems though... and the engine is going to have to be broken down... as he is subject to another SB which cont eng has put out reguarding valve problems. If you have valves or cyc or got a new rebuilt engine in 1996 to present... you need to contact Cont engn and find out if your engine is one of the effected ones. Need more info... write and I will try and help... skysmith is another source of information on the subject. G.M> 337club
Tony Portella asked
I'm in Florida.. how can i find who would have the equipment to set my fuel flow and pressure etc..??? in the south east???
Gmas replied
I would think that you should be able to locate a good fuel injection shop and have them refer you to someone local... if not them... to check your fuel system out. They either have a flow bench or calibrate the shops equipment that will be used to check your system... They need to be able to check it on the plane after checking the rest of the system out... the shop will want to make sure the injectors are clean .... Most of the shops will either use the test set manufactured by Aero Test Inc. called the M-ATM-C Porta test unit... P/N 630045-20 ATM-C. This unit can test anything on the system... If your mechanic does not have this information then I would suggest that you ask him how he does your annual withou out it. Continental has just reciently come out with a new Cat 4 Service Information Directive on this subject. Called SID-97-3 which superseeds all other SB on the subject. Its title is PROCEDURES AND SPECS FOR ADJUSTMENTO OF tcm CONTINUOUS FLOW FUEL INJECTION SYSTEMS... They are taking this serious.... As the compliance is at ENGINE INSTALLATION, 100 HR/ANNUAL INSPECTION, FUEL SYSTEM COMPONENT REPLACEMENT OR AS REQUIRED (if operation is not within spefications) YOUR MECHANIC NEEDS TO GET THIS LITTLE GEM... IF HE IS TO SERVICE YOUR PLANE CORRECTLY.... If he passes your suggestion off... find another mechanic.. hope this helps... fly safe G.M> 337 Club.
Hoses
Paul Sharp said
I would like to report for the benefit of other owners that I took the advice of another contributor here for my recent annual, and bought a set of engine hoses from:
PHT (Precision Hose Technology)
Mike 800-331-5946
The hoses were great. 3 had to be returned to get the right length, but the company returned the correct versions promptly, at no extra charge. The hoses had all the stainless-steel stuff and the high- temperature covering, and cost me about $850 for a full set (rear engine - 1967 turbo model).
Considering what the shop had intended to do - send the old hoses to a place they had always dealt with in the past who matches the lengths and bends and then returns a new set - which by their own words usually cost about $2000 (all figures just for hoses - no labor time), I saved a bundle and am happy with how it went. The people were polite, nice to deal with, and provided the product in a timely manner.
Ernie Martin replied
I was the one who steered you to Mike and I wonder what recommendation you and others (you there GMAs?) have on the high-temperature covering (I bought for the front engine last year without the covering but I'm getting ready to get them for the rear engine). Mike says that the original eqpt. hoses and the ones you get now from Cessna don't have the covering and his arguments for the coverings didn't seem that compelling. Last time I based my decision on those two factors, but now I'm hoping GMAs, you and others can add their thoughts. BTW I'm in Miami, where, of course, it's hot.
Gmas replied
We recomend the stratoflex brand of hose.. that has the sort of brown covering... We get some of them from Sacramento Sky ranch... contact John... on the internet... and mention the club... ask for a discount... while they are more expensive... they last a lifetime... and are warrented ... we have not had a return.. or a defect.. but, the shop is great and if you have any problems with the hoses.. they stand behind them... and they are certified.. you still have to have them inspected every 5 years but, if they fail the test.. you get new ones.. the hose meets all the fire requirement as well as it is smaller in dia.. than the 3003 with the added fire sleave .... red stuff... which covers the hose... and guess what happens when you get a leak... inside the outside hose... .... the brown can be used for fuel and oil... are direct replacements... while stratoflex and others make different hoses... we like the stratoflex brown... it keeps the cold cold and the hot hot... and last a lifetime...
Ernie Martin asked further
Thanks GMAs for your response, but specifically what's the consensus on the high-temperature covering (the red/orange outer plastic)? I'm going to order the Stratoflex-brand hose, but I haven't yet heard persuasive arguments for the high-temp covering, and the original hoses and the ones Cessna sells don't have the high-temp covering. Is the extra money worth it?
Paul Sharp added
Here's my thinking, FWIW: I asked the mechanics about it. They felt that in general it was worth having the extra fire-covering.
In this particular case, where it's a rear engine, and where you can't see it, they especially felt it was a good idea. I thought about it and decided I felt the same. If I had a fire in the front I'd be more likely to at least see it. So since this set was for the rear engine, I added the fire covering.
Gmas replied
Ernie... well you could use the old 303 hose that originally came on the bird...and it is still made... stratoflex 111 is another which is the counterpart... but, here is why the new fire resistant hose is used... first off... it is a better hose that takes the heat and cooling... second it is a lifetime guarentee... if it goes bad develops a leak..ya take it back and they repalce it... third.. the new FAA rules for fire protection in the engine compartment reads as follows...
Department of Transportation Federal Aviation Administration Aircraft Certification Service Washington, DC
1/13/61 Part 514 - Technical Standard Orders for Aircraft Materials, Parts, Processes, and Appliances
Part 514 contains minimum performance standards and specifications of materials, parts, processes, and appliances used in aircraft and implements the provisions of sections 3.18, 4a.31, 4b.18, 6.18 and 7.18 of the Civil Air Regulations. The regulation uses the Technical Standard Order system which, in brief, provides for FAA-industry cooperation in the development of performance standards and specifications which are adopted by the Administrator as Technical Standard Orders, and a form of self-regulation by industry in demonstrating compliance with these orders.
SUBPART A -- GENERAL
This subpart provides, in part, that a manufacturer of an aircraft material, part, process, or appliance for which standards are established in Subpart B, prior to its distribution for use on a civil aircraft of the United States, shall furnish a written statement of conformance certifying that the material, part, process, or appliance meets the applicable performance standards established in this part. The statement of conformance must be signed by a person duly authorized by the manufacturer, and furnished to the Chief, Engineering and Manufacturing Division, Bureau of Flight Standards, Federal Aviation Agency, Washington 25, D. C.
Subpart A also requires appropriate marking of materials, parts, processes, and appliances as follows:
(a) Name and address of the manufacturer responsible for compliance,
(b) Equipment name, or type or model designation,
(c) Weight to the nearest pound and fraction thereof,
(d) Serial number and/or date of manufacture, and
(e) Applicable Technical Standard Order (TSO) number.
In addition, Subpart A provides that no deviation will be granted from the performance standards established in Subpart B, and that the Administrator may take appropriate action in the event of noncompliance with Part 514.
SUBPART B § 514.52 Fuel and engine oil system hose assemblies (rubber or tetrafluoroethylene tube and wire braid construction) - TSO-C53a-- (a) Applicability -- (1) Minimum performance standards. Minimum performance standards are hereby established for new models of fuel and engine oil system hose assemblies1 of the following types manufactured on or after February 1, 1961, which are to be used on civil aircraft of the United States. Fuel and engine oil system hose assemblies of the following types approved prior to February 1, 1961, may continue to be manufactured under the provisions of their original approval.
(i) Type A. Non-fire-resistant "normal" temperature hose assemblies which are intended to be used in locations outside fire zones where the fluid and ambient air temperatures do not exceed 250°F.
(ii) Type B. Non-fire-resistant "high" temperature hose assemblies which are intended to be used in locations outside fire zones where the fluid and ambient air temperatures do not exceed 450°F.
(iii) Type C. Fire-resistant "normal" temperature hose assemblies which are intended to be used in locations within fire zones where the fluid and ambient air temperatures do not exceed 250°F.
(iv) Type D. Fire-resistant "high" temperature hose assemblies which are intended to be used in locations within fire zones where the fluid and ambient air temperatures do not exceed 450°F.
(a) New models shall comply with the following minimum requirements. Three samples of each size shall be tested. (1) Type A hose assemblies shall comply with the "3.3 Performance" section requirements of Specification MIL-H-8795A, dated July 25, 1958, 2/ except as noted in subparagraph (2) of this paragraph. The hose incorporated therein shall conform to "3.6 Performance" section of Specification MIL-H-8794A, dated July 25, 1958,2 except as noted in subparagraph (2) of this paragraph. (2) Type B hose assemblies shall comply with the "3.6 Performance" section requirements of Specification MIL-H-25579 (USAF) Amendment 2, dated March 19, 1959, 2/ except as noted in subparagraph (2) of this paragraph. (3) Type C hose assemblies shall comply with the above requirements for Type A hose assemblies and in addition shall pass the fire test described in subparagraph (3) of this paragraph. (4) Type D hose assemblies shall comply with the above requirements for Type B hose assemblies and in addition shall pass the fire test described in subparagraph (3) of this paragraph. (2) Exceptions. (i) Type A hose assemblies are not required to comply with sections 3.6.1.2 and 3.6.2.7 of Specification MIL-H-8794A. The operating and proof pressures referred to in Table 1 of that specification shall be those values listed in the "Fuel" column thereof. The burst pressures to be utilized shall be twice the proof pressures listed in the "Fuel" column in Table 1. The foregoing shall likewise apply in showing compliance with Specification MIL-H-8795A. (ii) Type B hose assemblies are not required to comply with sections 3.6.5, 3.6.7 and 3.6.10 of Specification MIL-H-25579 (USAF). The burst pressures to be utilized shall be twice the proof pressures listed in Table 1 of that specification. (3) Fire test procedure and requirements. A description of the standard fire test apparatus and its use is in FAA "Standard Fire Test Apparatus and Procedure" (Power Plant Engineering Report No. 3)3 . The use of a protective sleeve over the hose and/or end fittings is permitted to facilitate compliance with the fire test requirements. Sleeves or covers shall be secured to the hose assembly so that fire-resistant properties will be maintained. (i) Oil pressure during fire test: Type C hose assemblies - the operating pressure specified in the "Fuel" column of Table 1 in Specification MIL-H-8795A. Type D hose assemblies - the operating pressure specified in Table 1 of Specification MIL-H-25579 (USAF). (ii) Oil flow rate: 5x(Hose assembly actual ID in inches)2 . (Example: Flow rate for -16 size = 5 x (7/8)2 = 3.8 GPM) (iii) Duration: 5 minutes. (iv) Criteria for acceptability: The hose assembly shall be considered acceptable if it complies with these test conditions without evidence of leakage. (b) Marking. The markings required are specified in Subpart A, with the following exceptions: (1) Trademark may be used in lieu of name, and manufacturer's address is not required. (2) In lieu of the weight specified in paragraph (c) of Subpart A, the size of the hose assembly shall be shown. (3) The Applicable TSO number shall be followed immediately by the appropriate type designation, as TSO-C53-Type B. Where a protective sleeve is employed, the information should be legibly stamped on a steel (or other fireproof) band securely affixed to the hose assembly. (c) Data requirements. The following information and data should be submitted with the letter of conformance. (1) One copy of drawing showing the hose assembly constructions, materials, part numbers and the recommended maximum and minimum fluid and ambient temperatures for continuous operation. The following data should be shown for each size: Proof and burst pressure (minimum), Operating pressure (maximum), Bending radius (minimum). (2) One copy of any installation instructions and/or other pertinent information (may be shown on drawing). (d) Effective date. February 1, 1961.
So what does this mean to you... well it means that the hose is located within a fire zone.. engine compartment... and to meet the new standards should meet the fire protection regulation... and righfully so... as a fire is the last thing you want in an engine compartment... especally with fuel... spewing all over the place... Now it does say you can use the hose that the manuafacture put on the craft at the time of manufacture... but now a days we meet or exceed the rating... with exceeding being the key word here.... to make safe... or provide a greater degree of safety... from fire... the stratoflex hose meet the new tech. bill...
Next what about the heat... well it seems that you can put a blowtourch to the outside of the hose and the fuel inside stays nice and cool... a benifit to the fuel supply hose which runs across the top of the engine... back to the fuel pump... simply it keeps it from having vaporlocking problems...
and for the Turbo/press.. guys and gals... it is a must that this hose be put on.. to help ya from runing the boost electric pump... when you go way up their... we have seen a dramatic change just by changing hoses... and keeping the radiant heet from the engine from effecting the hose... strange as it seems...
Lets see did I miss anything... oh ya size... and inspection... on the other hoses.. that came on the bird... if you have a leak.. you have gas all over... if you have the other hoses... that are covered with fire sleve (red over hose stuff.. with clamps at both ends.. you make a baloon out of the outer sleeve... and its a matter of time before it starts leaking... the size of the red over sleve stuff is about 3 time what the original hose is... making it difficult to work with... the brown hose.. is only a little bigger...than the original... and the silicon outside covering... does not abrade any alu parts or other hoses.. if it is in contact .. like the armor or SS covered hoses do...
Is it worth the money... Hmmm let me think here... yes if you value your life and your family... I hear it gets real hot when the airplane turns to a fireball coming down... and no if you want to take a chance and stay with the old technology... really the choice is yours to evaluate... and decide how much its worth to you... a couple of bucks more now... or becoming a roman candle in the sky later... because the original hoses are only rubber... and will harden real fast with the new gas... vibration does the rest to break it open... see if you can get a mechanic to show you what happens to the old 303 fuel lines when you bend 'em... yep they will break in half... even though they seem good.. they get as hard as rocks.... hope this helps G.M>
Ernie Martin replied
Thanks to both of you for your inputs. Good points. Ended up doing as you suggested: the Stratoflex Teflon with the stainless steel braid covering, and then the optional outer fire/heat sleeve (for more info on this red/orange shield, go to the link shown below; click on "2650 Firesleeve" for picture and description, or on "Firesleeve" for specifications).
Gmas added further
Hmmmm but, the red is not what we use... we use the brown because it is all one hose... no band clamps.. etc...but, it is the same inside... tf hose armored but, has a brown silicone rubber cooked on the outside... I transfered a section of the hoses to the web see ... hoses.. G.M>
Liquid cooled engine
M. Brady asked
I have always thought that the Skymaster was the prefect platform for the Cont. Liquid cooled engines. Is and STC available, in the works, being mulled over??
Bob McGrath replied
At least one is flying. I don't want to give you wrong info about where and who so I'll look it up when I get a chance and send another note.
G.M>337 Skymasters Club added
Their have been two that I know of that had liquid cooled engines added to the back of them... One being used as the cont test bed for the new two stroke desiel engine.. the other was a gent who put a buick alum bock engine in the back... the latter was restricted to the inland valley and was eventually sold for scrap as the owner had to turn in the airworthyness cert and lost the aircrafts type certificate... to become experimental.. and when he wanted to restore it back to the origanal condition.. the faa required the full crash test stuff... which made it prohibitive... another engine that was tested in the back was the 550L up at washington but, I never heard the outcome of it... nor the one that tryed to put Franklins in place of the cont. several have gone to the IO47Os' I think raley tryed to get the liquid engine in the super skymaster also... but, he had a stroke before he could finish and almost lost the company... I think he finally went broke... Those are the only ones that I know of that have tried to change the engines for the liquid cooled... Cont is not talking bout the new desiel two stroke engine... but your right.. it would lend itself nicely into the skymaster... and would get rid of the air scoop that is on top... and the cowel flap doors.. I have been told that once they get along further with nasa that they would send some pix of the aircraft that they test it in.. and hinted that the skymaster would be one... with the engine put intothe rear... for a test bed... it should be able to run on Jet A... and put out 240hp... but, its two stroke with a blower .... and is said to have better performance... and.... longer life.... Hmmmmm....
Aviation Enterprises, White's Creek, Tenn. (aviation.ent@juno.com) were advertizing a 350 hp liquid cooled V-8 installation. Haven't seen their ad for a while
Long Term Storage
Tony P asked
How to and what kind oil is to be used to preserve an engine for long term storage. Any coments would be appreciated Tony P.
J.R. Prukop replied
The Cessna Service Manual contains the complete procedure. For the 1973 through 1980 Model Year of the Pressurized Skymaster Series, see Section 2, "Ground Handling, Servicing, Cleaning, Lubrication and Inspection."
Gmas also replied
Tony... their is some oil that Shell is promoting as a storage oil... cost about the same as 100w... and basicly you change oil.. put this in in place of the old oil...and then run the engine... for about 5 min.. shut down and remove the spark plugs.. sqt a small amount in the engine cyc and pull through then replace the plugs and tag the engine... they claim that you can store it for about a year without damage... make sure you relieve the mag springs.. stop just after they click... with the props horztal and then pulll it through once a week... plug the air intakes in the cowlings to keep the birds out.. and thats about all you can do...
but, why would you want to store it in the first place... unless its because of the snow fly... g.M>
Marvel Mystery Oil
J. R. Prukop asked
What words of wisdom might you be able to offer regarding this fuel additive for the top-end of mixmasters .... I have a friend who uses this stuff in a Cherokee 235 Pathfinder, but he's using it in conjunction with the AUTO Gas STC, which might make sense. With 100LL being a more refined fuel, what about the use of this Marvel Mystery Oil, or is this another gimmick/snake oil elixor?
Gmas replied
Well it used to be.. thought that the top cyc lub was the thing to have... but, Mar oil is mostly a solvent and 2wt oil... the solvent would get rid of the varnish and the oil would lub and keep things from sticking... Then they found out that it actually was working the other way.... The intake valve on the aircraft engine actually gets too much oil... that ends up getting sucked up into the intake pipe... and as the guides wear... they oil comsumption of the engine actually can be contrubited to the oil going by the intake valve... and of course it ends up in the cyc.... so the addition of marv oil really does not do much more.... execpt add to the oil supply... Now as far as using auto gas... I wouldn't unless you like to practice your emergency landings... when we used to have lead and reg gas... things were good ... but, now they throw everything but the sink into the fuel... for cars and each week it changes... formulation... so to say it is stable ... OK... AVGAS... on the other hand is kinda made to a standard... and contains lead... which is needed to protect the alu parts from the corosion action that the burnt fuel and water vapor make... which we have discussed before on the web... We have seen auto gas actually destroy a lot of rubber parts like fuel pressure diaphrams... and harden hoses up a whole lot quicker... because of the junk that the add to it... so the costs savings just is not their... when you use autofuel....as well as the reliability...
J. R. Prukop relpied
Thanks for the heads-up on the 'mystery' oil and the autogas. I was actually inquiring for a friend who has a 1974 Piper 235 Pathfinder with a fresh factory reman ... the fellow he bought it from was using this stuff, plus he already had the STC for the MoGas ... but I thought the information would be good for the other 337 drivers to know about. What you said about the stability and the cleanliness and/or refined quality of the AvGas is a definite plus ... wouldn't think of using anything else in the Skymaster ... but you know how some of these "weekend" putters are ... always experimenting and buying the 'gadgets'. C'mon, the plane just won't 'fly' unless you have some 'mystery' oil and Edsel fuel!! I told him when he bought the Piper that he should stick with AvGas. This just confirms my suspicions; I knew it was 'dirty' fuel.
Rear engine
Markus Ewald asked
What is the reason (if there is one) for the (sometimes) earlier replacement or the rear-engine?
Scott "Sky" Smith replied
Education or the lack of it puts unusual stress on the rear engine.
It does not get the same air flow, but if mixture and cowl flaps are used correctly you can achieve TBO or more without difficulty.
Steve Hausmann asked another question about the rear engine when he asked
I am looking to purchase a model 336. There are very few. The rugged design of the skymaster combined with the fixed gear seems to be a natural for "bush" type operations. My main question is: rear engine airflow/cooling, is it worse than the model 337 or is it just a matter of operating technique?
gmas replied
Yes the 336 had /has a problem with cooling... the later 337 had a large scoop placed on top and this took care of the problem... the 336 relied on a fan which was attached to the crankshaft... needles to say a lose bolt or screw would make a mess of the fan works... If I might suggest taking a 337 early.. somewhere around 1965-69 because they are lighter and have a better payload with a door...in the back... and having the escapement fixed to only be down and welded... I think you would be better off than with a 336... basicly you are making a 336 out of your 337 - G.M
Rear engine cooling
gmas posted the following information
I just finished overhauling a 337 rear engine because of what we though could have been plugged injectors... or else the pilot ran the engine too lean and caused detonation... After giving the engine back to the owner... he had his mechanic install it... and brought it by the following week to have the fuel system checked and adjusted...
What happened next was somewhat shocking to him ... When he opened the back coweling up... the first thing I noticed was that the rear baffeling was not even contacting the No. 5 cyc fins... it was bent back at about a 45 deg angle and left a gapping slot about 1 inch wide and the full width of the baffel (5inches)... I went to the other side No. 6 cyc... and the same had occured their... I then looked at the baffel seals... or where they used to be... When I questioned him about these items... and asked if he thought that they were important... he replied.... well hey it has that big scoop up on top and it should make up for that.... little leak... Hmmmm I explaned... that it was no little leak and that if it were the same on the other engine... could have possiably been the reasion he was running hot and had a short engine life. We did a little sheet metal work to repair the problems around the baffeling... by adding stiffneers and replaced the baffel seals... cost around 20 bucks U.S. he was back in the air.... It seems that this area is a common problem... that cessna did not address too well... you may want to check your mixmaster and see if you have the same... If you have a 1/4 inch gap around anything... it is getting too big... the engine was designed to have a pressure on the top deck or as we call it the plentium... please make sure that your rear or fwd engine does have all the seals working... to insure proper cooling. With these in place you will be surprised that the rear engine will run as cool as the fwd. Just like this one does now... Fly Safe... G.M>
In another posting to the message board sdill asked
I'm a new P337G owner with a Riley conversion. Just got back from a trip, San Diego -Quebec, and loved the performance. I noticed, however, the rear engine oil temp continually runnung about 30 degrees warmer than the front, while the cylinder head temps seemed close. At altitude, 12 to 16,000, the rear oil temp was usually about 210. I tried to keep the engines at 1610 - 1620 TIT. I know I could cool the rear engine more with cowl flaps or richer mixture, but don't really want to do that.Also, during hot days in So. Calif., I have a tough time keeping the oil temp away from the 220 degree level, not good I think!
Any comments. Thanks
J C Buehler replied
You may be stuck with the problem. The 337, particularly the P model with the conversion, has a reputation for rear-engine temp concerns. The situation you described is quite normal in the type and can best be addressed by minute adjustments to the rear cowl flaps and a slight richen of mixture. Unfortunately, the noise level will increase, but that's a small price to pay. You may wish to have the rear eng rubber baffling checked for security, fit, cracks, etc.. Worn or loose baffling can contibute to higher temps. Good luck
GM @337 Club... added
Your problem is one that we see at the club all the time... Their are many things that you can do to bring the temp back in line... As the other respondant said ... first check the baffeling... both flexiable and fixed... for cracks and areas of air passage around the plentum area... anyting over 1/4 inch.. is too much... check the guage itself...for accurcy... Then check the varitherm... in the oil cooler itself... we have found that sometimes these things stick or are out of specs... Fuel pressure/fuel temp... mag timing ignition wires are but a few things that could be giving you problems... Riley should be able to help you get your back engine to run at the same temp as the forward I also strongly recomend that you seek out the services of a good personal mechanic... who is/or does work on your type of plane... if your mechanic is not up on mixmasters you may want to have him contact us at the club.... we strongly suggest that.
Rear Engine Failure & A/C
Charlie Slaton asked
I just bought 75 337G - 20EC based at Addison in Dallas. I'm trying to network with any 337 owners in Texas. Couple of things 1) anyone outthere figured a reliable method/instrument/?? for alerts/monitoring of rear engine failures? With an instructor with over 600 hours in C337, we lost our rear engine on takeoff at Addison, carrier type landing at the north end of the field just short of the fence, insurance gets to take down the engine due to a prop strike on the back, but now that I've experienced a single enging takeoff attempt, I'd like a little more warning. 2) Anyone put in a J&B airconditioner on (I figured while the back engine is out it would be a good time to explore). Thanks
Ernie Martin replied
One of the critical Airworthiness Directives for the 337 is 71-17-08 to avoid precisely what happened to you. Among other things, it requires that the flight procedures (and check list) be modified so that take-off is initiated by advancing the throttle of the rear engine AND not advancing the front engine throttle until satisfactory rear-engine power has been confirmed. A placard with this requirement (LEAD TAKE-OFF WITH REAR ENGINE POWER -- CHECK RPM AND FUEL FLOW) must be permanently installed near the tachometer, and this point was the one most drilled into me by my instructor when I started flying my 337. In fact, in addition to this procedure, I never commence rotation until I've glanced at the tachometer and fuel flow guage to confirm all is OK. If you include this in your check list (and on mine it's in bold red letters), I don't think you need any rear-engine-out alert.
Gmas also replied by saying
Yep... take my advise... fly higher and you will get cooler air... if on the ground.. don't take so long.. to get into the air... putting AC on the AC will only give you problems you really don't want... that is why they don't make 'em anymore... otherwise cessna would have put it on...
As to engine failure... bet you had to step on the rudder pedal when the engine quit.. huh..... guess what your first clue was... second if you want to make sure the engines are turning and burning... look at the EGT gage... as both the fuel, RPM and MP will only change slightly from a operating engine to a non-operating one...
I had the guy from a mag. once come ask about the engine out.. and I played fox with him... he being a big writer and all... was heavy into the rear engine forget its on thing... and was well versed by someone else who told him how it is dangerious... who aparently never had it go out.... Well we got into the plane... and on the way out I asked him again about the story he told.. and was writing about.. while he was talking I reached up and shut the rear fuel off... I figured no matter what I said he though me just a dumb mechanic... Now it takes about 45 seconds for the engine to run out of fuel... and knowing this... I told the tower we wanted the option for the take off... they know about my methods of teaching... these well versed people.. and agreeded... he said .. what.. and I said lets go... so he pushed up the power... about half way down the runway.. befor we got off the ground... the rear engine quit... I saw the EGT hit the floor.. he didn't because he was still too busy talking and impressing me... when suddenly he said... hey you standing on the left rudder... nope not me.. I said.. and he said something is wrong... as the plane is heading for the left side of the runway... I reached over and pulled the power on the good engine and then gave it back to him... wow he said what happened... Hmmmm I answered... gee I don't know... he quickly scaned the guages and then said the rear engine is out... Yep I replied... think you could take off and not know the engine was not running... but, did he write one word of his experance... nope... and when I called him up after reading the article... and not seeing it... he said his publisher told him not to put it in... great huh...
So you should have also experanced the rudder thingiee... and you should always remember that you are flying a twin.... practiceing the acellerated stops... and engine out is part of your takeoff... pre-flight requirement... do you practice it... or did this one catch you off guard... smile.... always.. always check the EGT befor liftoff... if its not right... or somewhat normal... you might want to stay on the ground... it is the best indicator you have and no other will replace it... and yes it is required to be in the skymaster ... it was certified with it... as all twins are... G.M>
Ernie Martin replied
Thanks, GMAs, for the anecdote. Will start looking principally at EGT before rotation. Didn't know about the tendency to veer left if rear engine quits. Whay's the principal reason for this, the front prop spinning hard and the rear one slowing down?
Gmas replied
NO... its called P factor...
Charlie Slaton added
Had a lot that I was noticing at the time... Thanks for the advice on the EGTs, and it did surprise me (had an instructor on board for check-out).
Follow-up: got a test prop back (rear prop strike from hard landing), engine fired up and ran, roughly, but ran. Showed lean at idle. It's being torn down for a crank inspection as we speak, will probably have it zeroed (only 134 hours SMOH). Once we figure out what happened, I'll post...
Rear turbo losing power @ altitude
Marvin Koursh asked
Rear turbo on pressurized 337 (1973) loses power starting at 13,000 feet. New turbo installed, exhaust leaks fixed. At approximately 13,000 manifold pressure begins to drop until at 17,000 or 18,000 manifold pressure down by ten inches.
Surprisingly, however, increasing rpm on rear engine from 2500 to 2525 or 2550 immediately brings back power to 33 inches proving the power is there.
Capping off the wastegate does not change anything. Controller replaced, wastegate overhauled. Still with same symptoms.
Any ideas? Would appreciate any and all help. Thanks in advance.
GM 337 Club... replied
Marvin... your problem is not with the waist gate or turbo controler... it is more in the fuel system... you are kinda vaporlocking... See the rear engine is mounted higher than the fwd one.. and the fuel pressure from the tank to the rear engine is lower. So the engine driven fuel pump looses its prime... if it is true.. try this.. when you get to 13000 and notice the pressure droping.... turn on the boost pump on to low for the rear engine.. the pressure should come back up.. both in fuel flow and MP... It seems that this problem hit Calif. several years ago... we think they changed the fuel formula and vapor pressure....by the way the engine is really running lean also... but it went past peak.... so you don't get a indication... how to fix it.. well we have A couple of things that we recomend if this is your problem... First of all the fuel lines... check the fuel supply lines (the big one) for leakage... check all the fittings for leakage... Next we look at the boost pump ... check it for leakage... and also the fuel stainer... O rings get old and leak... admitting air into the system...again any of the supply suction side of the fuel system is the problem.. . to check this shut the fuel off at the cabin... put a hand held vacuum pump on the line at the fuel pump... and check for leakage... I think that you will find your problem in the fuel supply system... We changed the supply hose.... we found that the ones made by Sacramento Sky ranch in Sacramento Ca. help... with one of the new stratoflex fireproof ones..they are brown in color and have the teflon interior hose... we are not really concerned here with the fire protection .. but, rather the heat insulation... to keep the fuel from getting so hot.. from the radiant heat of the engine... The next thing we do is look carefully at the fuel pump return orfice, mixture contol.. and pressure adjustment... here we make sure that the fuel pump will make the manufactures pressure and all but, we also look at the movement of fuel through the main feed line... idealy you want to have have half the fuel going to the engine and the other half going back to the tank... by keeping the flow up we can help prevent vapor locking in the line .... thats why when you increase the RPM... the engine comes back up... the fuel pump flow increases... hope this helps...
Dave Zavoina added
I had a similar problem on a Piper Seneca II, found out it was the aneroid bellows in the engine driven fuel pump. You could try watching your fuel flows and EGT's at atlitude to see if there is a difference. Might be of some help.
Tach generators (O-2)
Dave Zavoina posted this piece of advice
O-2 owners/mechanics, I came across something interesting this weekend on my O-2A and I'd like to pass it along to you for future reference. I had my rear engine tach-generator overhauled this week and put it on following my annual inspection, and upon run up, the rear tach indicator needle wound itself all the way around. I had put the right angle adapter on bass ackwards, and instead of reducing the generator by one half, I had doubled the RPM's, so that instead of producing 21 volts for the indicator, it had produced 42 volts. The Maintenance Manual does not address this, so keep a heads up.
Turbine Conversions
Dave Roberts asked
I am interested in any information on Cessna 337 Turbine Conversion.
I believe that Basler Turbine Conversions in Oshkosh are one of the companies performing conversions. I would be pleased if someone could help me with the folowing.
1 Are there any other companies converting c337's to turbine power?
2 Are there any web sites where I could research this subject further (history etc.)?
Ian Clapp replied
The only thing I know of is that Cessna made a prototype version of the O-2 called the O-2TT. It was powered by two 317 SHP Allison 250-B15's. I have no information about its performance other than the indication that the project was cancelled because of inappropriately high fuel consumption at low altitudes.
Turbo Induction Degradation
Louis asked
I have been noticing that the manifold max. manifold pressure on my TSIO-360-D engine has been gradually decreasing. The wastegate has been cleaned and it seems to be fully closing. There are no leaks in the manifold. Cylinder compression is no lower than 75. There seems to be some slack in the cam bushing at the manifold regulator which I am sending to be rebuilt. Hopefully this will allow full contact of the cam to the regulator but I was wondering if anyone else has experienced this sort of manifold pressure decrease.
gmas@ 337 club replied
Hmmmmm.... well here is my suggestion... if you do not See the MP change after you get your controller back I would check the fuel pump and the unmetered fuel pressure system .... It could be the diaphram and bellows in the fuel pump may be getting out of adjust or tired... As always... it helps to give all the other indications ... like the EGT/MP/RPM/Fuel Flow (pressure) Temps etc... To really check out your system... I recomend a test box mfg by Aero Test... I just finished a class on it and have found that it is a complete fuel system check in one box... and works great... If you can find a mechanic who has one... I recomend that you have your system checked at least once a year...(Cont in the SID 97-3 requires it)
Let us know what you find and if these suggestins work...
Louis replied
I thought about your theory and thought that it could be contributing to the problem. So what I did was at cruise level, 12,000 ft., I put the fuel pump on low, which I normally do anyway because of vapor lock. I saw no increase in the fuel flow and no increase in maniflod pressure, putting the fuel pump on high showed an increase in fuel flow but not manifold pressure. The controller has nearly 1/16" of play at the cam pushing. I think the cam is not pushing the piston on the controller in enough.
gmas replied further
Hmmmmm... yep.. but, the cam pushing on the controller... only works the waist gate.... the fuel and manafold pressure is controled... by the increase in MP When it pushes in on the piston... it cause the oil to be cut off to the waist gate controller...increases its pressure and thus causes the piston to close the waist gate.. causing more exhaust to go through the turbo... and increasing its output... So if it is the waist gate... controller... then you would not have MP boost on takeoff... and fuel flow would be down on the hi end... as the increase in MP causes the fuel pump to have a higher pressure on the unmeatered hi end... The diaphram on the other side of the turbo controller measures the MP and tries to force the piston back out.... to balance the system... If it was that part of the system you would see the MP gage fluctuate up and down... and the fuel will follow... No... I still say it is particular to your fuel pump... and vapor pressure... Have you checked the vapor return jet yet .... If it is plugged or gets dirt in it... you will be trying to pump the vapor too... instead of them being sent back to the tank through the return line... The fact that the test you did showed an increase in Fuel Pressure (fuel flow meter is a pressure gage)... and not an increase in MP... I would say it is still air in the system.... have your mechanic check the vapor return portion of the pump.... top 4 screws takes the cover off... new gasket needed... the jet is screwed in ... be careful not to bumb the threads... of the housing... it is al and soft soft... sometimes we grind a screwdriver's sides down to make sure it fits... unscrew.. and remove with magnet... clean... flush out the pump using the boost pump... and replace... by the way... we had one that had a similar problem to yours but, before we could get a hold of it... into the shop... the main fuel pump let go... seems the boost pump carbon vanes... which are now compositt... broke and ended up in the main fuel pump... taking it out too... so your problem might be starting in the boost pump... rear engine.. because the fuel filter is before the boost pump... forward engine has the boost pump before the filter... but, check the vapor jet... and let me know how it looked...
gmas then added
Hey just talked with the rep that works on turbos here in Calif... and he said that your probably right about the cam... it should not have much play... the linkage that conect it has just a little but not more than 1/32 to 1/16 inch... the cam should not be loose on the shaft... he thinks you might need to check that it is not comming apart... He is puzzled though about the part where you mentioned that the waist gate is closing all the way... and you are loseing MP pressure..... he is thinking that you should check to make sure it really is closing all the way... He's thinking that you might have some sludge in the WG actuator housing...... else the orfice in the housing (the one that is attached to the waist gate ...) is plugging up a little... also he mentioned one thing that I forgot... oil pressure... if it falls below 25 lbs... you will not get full actuator action... I assumed that you are pumping at least 40 lbs... To check full closure.. you can use a visual mark... on the arm and ground running... The shop name is Gary Main Turbo... and Gary says to give him a call if you need the controller reworked... he does all of our work...and is real good... G.M>
Louis replied
Hey GMAS, When the waist gate closes I DO get full manifold presuure. Even if the waste gate doesn't close, which happened once on the front engine, I still get normally aspirated manifold pressure. My problem is that I'm not getting BOOSTED maniflod pressure. There is a LOT of slack at the controller linkage and I really think this is the problem, although once it is rebuilt I'm gonna do your fuel pressure bit also just to be on the safe side. I'll let you know.
Louis... ya.. the controller will give you only the boost... and should work the actuator... If you look at the actuator... when the engine is running up.. the actuator should start to close the waist gate... Ok.. to test the system... WARNING... you are going to be around a moving prop... CAUTION is advised... as the SPINNING prop can be leathel and result in injury and/or death... keeping that in mind... Here at the club shop...we remove the actuator outlet hose and take a tubing cap (AN 929) that fits the outlet of the actuatior... so that the oil pressure is blocked from going to the controller... by doing this we are simulating a full turbo boost condition... starting the engine will cause the oil pressure to make the actuator go to full closure... standing out side and watching (mind the prop) the engine.. you should see it go to full closure right away... noting the open and closed arm position... at idle up to 1200 rpm you will not get full boost as the flow of exhaust is low... you should get turbo boost... as the engine is run up.. were careful here because the turbo pressure can get up their more quickly as the rpm goes up... the turbo becomes more alive... We are able to control it by the throttle... manually.... you will not be able to push the throttle full on because the turbo will spool up and make the engine go to full power... a lot quicker than before you should see the indication on the MP gage... be careful not to let it go over red line... so go slow...on the throttle and give the turbo time to come up to speed... you can not hurt the system... as the controller does this normally... except the controller opens and will keep you from over boosting... if you go over red line... you can damage the engine.. and it is not advised... to allow the MP to do that. This is for system test only... you should not and do not fly the plane... If you do not get full MP... or a boost... then the controller is not the problem and the actuator or turbo is... it should be removed and cleaned.. their is a small piece of tubing 1/8 inch dia and about 1/2 inch long...which is pressed inside that makes up the orfice... a common problem because the oil is not filtered at the source point... a small piece of carbon gets logged in it.. and blocks the oil from getting in to work the actuator... So the system works this way... oil pressure is supplied right from the oil pump in the engine... by hose to the actuator... which has a small orfice in it... that allows a small amount of oil in at a time... to a chamber that contains a piston and a spring... the outlet... of the actuator goes to the controller... where depending on the MP setting by the throttle allows the oil to leak back to the engine... Low power setting... causes the controller to open fully... and bleed off the oil pressure... with no oil pressure the spring in the actuatior openens the waist gate... High power cause the controller to close off the oil leak and the pressure builds in the actuator...causing the piston to push aginst the spring and start closing the waist gate...(bypass) which cause the turbo to spool up in RPM causing the compressor side to make more pressure.... which is fed back to the engine intake... thus turbo boost pressure.... a sample of this pressure is fed back to the controller and the engine driven fuel pump... to maintain the power level set by the throttle... Again have a licensed person preform all work and test on this system..... before flight.... when you put it back togeather... I think you will find which item is bad... If the turbo is not working... then you are right you only get normal air... but, because the compression ratio on the engine is lower for a turbo... you will not get much over 175 to 180 hp... (less than 65% power) if you need help.. let me know where you are located and we will see if we can get you some help... else at our shop... Hope this helps... G.M> Keep me posted.. as to your findings.. Fly Safe.
