Rear Engine wants to Die!

[side241]

Hi guys, and thanks for all the great info.
Well, just made another rount trip to work (1 hr each way), and sure enough the rear engine showed the same loss of power. It is 100 degrees on ground, so its pretty hot, but thought the insulated fuel line would help.

I also rutinely run the aux pump when on aux tank, and any time after it has an incident of power loss. My concern has always been that the elec. fuel pump was probably not designed to run for hours continuosly all the time. With my luck, just when I need it it will fail from all the extra use.

Anyone else feel the same, or should I relax and use the elec fuel pump w/o worries.

Ben

[kevin]

I feel the same as you about continous use of the electric pump. If it were my airplane, I would continue to work to find the problem, not just keep using the electric pump.

One opinion, FWIW.

Kevin

[Walter Atkinson]

According to the manufacturer of the boost pumps, the electric boost pumps are made for continuous operation. I do not worry about using them to suppress vapor. That's one BIG reason they are there. I've been using one like that for a loooong time. Not yet had one fail, but I've stopped a lot of vapor problems by using it. Allowing vapor lock to continue has the same effcet as leaning the mixture inappropriately. That can destroy cylinders.

We know what the problem is. Insulating fuel lines won't hurt, but is not the answer. It's the engine -driven fuel pump being too hot. It is insufficiently baffled. We're working on an STC'd solution. Cool the pump and there will be no problem (easier said than done). Use the boost pump and the problem will be lessened.

[kevin]

Lots of folks fly T337s in hot weather at 7500' without this problem. I do not believe we know what the problem is, nor that an STC is necessarily needed to fix it.

Running with the boost pump on all the time is not normal for this aircraft. It may be normal in the aircraft you normally fly.

Kevin

[SkyKing]

No thanks. I think I'll retain my $450+ a-whack AUXILLIARY fuel pumps for their intended purposes... and only 'as needed' per the POH. I guess WA has never experienced a failed carbon vane in one of those puppies bust off and little particles go whacking around in the engine. Yah... my wheel bearings were designed for continuous operation too! What a hoot.

Seems the key phrase everyone is missing is "CONTINUOUS-FLOW fuel injection system"... ya think there might be a problem with the F-L-O-W??? Hhhhmmmm.

Oh... and think about this: If Cessna's R&D team really thought there was a 'problem' with the engine driven fuel pump getting warm, erghhh, I mean 'HOT'... HEY... they wouldn't have put it on the damned engine!!! Yep, but there's always snake-oil to sell... think about it.

Of course, maybe them Beech planes weren't quite R&D'd as good as Cessna. Ya think? And besides, the Beech has to pump fuel UP from the wing... Beech forgot all about 'gravity'!!! Maybe that's why them V-tails keep falling off.

SkyKing

[SkyKing]

For those of you with 1973 or later 337's, it might be a good time to review Section 7 of your POH -- the one entitled {Airplane & Systems Descriptions} and in particular the section on FUEL SYSTEMS. The LAST THREE paragraphs really lay it out for use of the AUX pumps. Hey by golly, there must be a reason they call it an 'AUXILLIARY' pump... no kidding!!!

And I didn't mean to exclude all of you pre-1973 Skymaster drivers... it's just that the post-1973 POH manuals were standardized format so that we can all be on the same page. With all of the different tanking arrangements and vapor return lines, a review of your specific POH and/or service manual section on the fuel system is a MUST-DO in diagnosing problems.

SkyKing

[Walter Atkinson]

SkyKing:

**Oh... and think about this: If Cessna's R&D team really thought there was a 'problem' with the engine driven fuel pump getting warm, erghhh, I mean 'HOT'... HEY... they wouldn't have put it on the damned engine!!! Yep, but there's always snake-oil to sell... think about it. **

First, I'm not selling anything.

Second, you might want to do what I've seen done and put a few thermocouples on an engine-driven fuel pump and record the temperatures in flight before makind any big statements. I doubt you (or Cessna) have ever done that. TCM did put a cooling shroud on it, so they must think there's a reaosn to cool it. There is no need to argue about something that has been measured.

"One test is worth a thousand opinons... and a lot harder to get."

[SkyKing]

OH REALLY NUMBER ONE!? Exactly when did Cessna or TCM {as the case may be} put a shroud on the Skymaster engine driven fuel pump for testing the temp? Don't think so, as it has NEVER been an issue in the real world. Thermocouples? Why waste time and money on something that is definitely NOT the problem!

OH REALLY NUMBER TWO!? "First, I'm not selling anything." And, "We know what the problem is. Insulating fuel lines won't hurt, but is not the answer. It's the engine -driven fuel pump being too hot. It is insufficiently baffled. We're working on an STC'd solution. Cool the pump and there will be no problem (easier said than done).

Why would you be working on an STC, if you didn't plan on selling/marketing it? The Skymaster doesn't need the specified STC... period... paragraph... as there is NO heating problem with the engine driven fuel pumps on the 337 series. As they say on TeeVee, "Sorry, Charlie!" Find another fish to fry.

OH, but maybe you were referring to a different make & model airplane... like the Beech you own/fly... and of course that'd be like comparing apples to mandarine oranges.

SkyKing

[Walter Atkinson]

Well, SkyKing, my boy. We got the flight data today at about 4:30pm central time on the temp of the fuel pump.

You're wrong.

One thing I'll say for you is that you may not always be right, but you're never in doubt.

"One test is still worth a thousand opinions."

Good bye, Skymaster forum.

[Dave Underwood]

Walter, can you please provide the results of your tests. I occasionally see the fuel flow needles flicker and have long suspected heat somewhere being the problem. That is even with insulated hoses and pretty good baffles, but does go away with AUX pumps on low.

Comment: I think we all know that although Cessna had a great engineering department, they could only test over a realitively narrow range of curcumstances. Our real life experiences are always going to be a bit different.

Further comment on certain suggestions that continuous review and design refinement is not necessary because the original design is fine:

If review did not take place we would still be flying biplanes and computers would never have been invented. Nor would you ever hear about the massive recalls by various car manufactures, nor the positive safety related changes they bring. Nor would the FAA issue AD's or manufactures SB's.

I would suspect we would not have the standard of living we have today if it were not for people continuously challenging the status quo and working hard to make things better.

My two cents worth.

[WebMaster]

Originally posted by Dave Underwood


Further comment on certain suggestions that continuous review and design refinement is not necessary because the original design is fine:

If that were true, that the original design was fine, they would never have gone beyond a 337B.

Engineers are tinkerers, they like to make improvements. What is a good idea today may be a bad idea tomorrow. What was not possible yesterday, may be accepted practice today.

[Walter Atkinson]

The improved baffle design reduced the temperature of the fuel pump 21 degrees. That was enough to stop the vapor locking on a 100+ degree day. We hope to do even better.

It's all in the science.

Anyone interested in communicating with me on these types of subjects, please feel free to do so by private e-mail as I will no longer be visiting this forum. Thank you and I wish you all well.

[SkyKing]

Message removed by webmaster due to its insulting tone. Members of this board deserve politeness and respect in all the messages posted here.

Kevin
Webmaster

[SkyKing]

Message removed by webmaster due to its insulting tone. Members of this board deserve politeness and respect in all the messages posted here.

Kevin
Webmaster

[side241]

Just a quick note, since I started this whole thread. I have had the same problem addressed earlier on every flight this summer. I suspect that WA might be on to something, since we have just about tried everything else to solve the problem.

There is no evidence of fuel leak, and fuel system has been pressure checked for leaks.

If anyone has anything CONTRUCTIVE to say (there is enough kvetching and sarcasm from SK), I and anyone else having the same problems would be EAGER to hear them.
Thanks,
Ben