Home Forums Hunting & Shooting Hunter's Campfire Turbine A&P mechanics help needed. I’m asking everybody I know.

I’m sorry, this is not a relevant post for this forum, but at this point I’m willing to ask anybody and everybody for advice. There’s a large group of people here, maybe somebody has an idea for a problem I have. Here goes:

I fly a Learjet for a private owner. The engines are Honeywell TFE731–20BR. Roughly 20 minutes after takeoff, usually right before reaching FL430, I get a red EICAS and a red master warning, ‘RT ENGINE BLEED AIR’. Supposedly a leak in the bleed air system of the right engine. The entire bleed air detection system has been throughly inspected, the fire loop has been replaced. There is no bleed air leak. The red messages/warning continue to occur.

The light extinguishes when I turn off the rt bleed air and idle that engine for 20 seconds or so. The passengers don’t like it when they hear an engine rolling back at FL430, it scares them. The light goes out, I bring the engine back and the light won’t come back on till the next cycle.

The A&P who does the wrenching can’t figure it out, says, ‘don’t worry about it’.
I’m not worried, the owner is. I think it’s an EICAS computer glitch. Any experienced turbine A&P’s that might be here have any suggestions?

I told the owner that we are going to get to the bottom of it.

This place has an incredible depth and breadth of knowledge and experience but unfortunately in this case it’s not going to come from me. I was wondering though if you have contacted Lear and explained the problem? If it’s a software or computer issue I would think that Lear would have a record of that and a patch for the problem.

Good luck and safe flying Sir.

Oh yea, thanks for the reminder, I forgot to mention, Bombardier, the manufacturer, don’t know either.

I fly the 731 in another airframe, as a pilot you have to do what your doing because if you don’t and the problem is real then something is going to melt or burn not good! I would make them get to the bottom of it.

F..... that machine....

I'm staying my ass on the ground

Thanks. I kinda figured that would’ve been one of your first moves and I’d expect that Bombardier (Lear) would be of more help? Did they just blow you off?

Does it have a automatic or manual transmission?

My thoughts as well. Fact that it resolves when you throttle back and doesn't come back suggests electronic widgets gone amuck. Faint possibility it's the bleed air valve/band function, but I'm skeptical.

As F-4s got older, on occasion we would get an intermittent FIRE light 😳and I think they eventually attributed them to some corrosion at the connection points in the detection elements. It sounds like that aspect has already been investigated though.

It’s hard to ignore a red light.

Perhaps using more bleed air from that side because of fault on other engine?

Not an A&P, but I do work in avionics and have for a considerable spell. Where there's a persistent issue like this one, the thing not to do is shrug and tell the flight crew to ignore the warnings. It's caused by something, and whatever it is should be resolved. Peoples' lives are at stake.

I wouldn't let that mechanic touch my airplane.

edit: if your AHRS systems are 142185-3101s and if they ever give you problems, or you just have questions, PM me.

I just want to say up front I am no jet engine expert; but, There has to be at least one sensor of some type (mechanical or digital) to detect the "leak" in the bleed air and set off the master caution. (Yes, you know that and so does your mechanic) If the sensor(s) checks out as good and short of replacing them (hanging parts) it could be an EICAS computer. I was not an engine guy so I'm just spitballling but I'm more inclined to think it's a sensor and not a computer especially since you are not getting the warning on the left engine. Of course, you can always hang a new computer but I'm betting the sensors are less expensive than a computer. When we transitioned to the Blackhawks we had sensor issues occasionally but I don't ever recall a "computer" failing. (EECU)

It's just that the fault repeats itself at a certain altitude and once the system is recycled (engine idled) everything is happy. I am inclined to believe it is a pressure sensitive (altitude) sensor that has to catch up with itself. I'm guessing your rate of climb is better than 2000 feet a minute even at altitude and something in a sensor is slow like a bellows (mechanical) or a resister that catches up with itself when you go to idle the sensor acclimates to the altitude.

Just my thoughts.

kwg

Not familiar with Honeywell… I work on GE T700 equipped helicopters. I am an A&P but by no means a tweek. From the hip, I would start by (re)-metering power to the sensor and the valve. Let’s see if we can isolate a wire grounding in the harness. If parts are available, I would then slave a new valve and/or sensor and perform a FCF. I doubt you will need to replace the EICAS computer but you have an AVI gremlin, no doubt.

haverluk, I think you're onto something. The problem happens at altitude. If the problem was a bleed air leak it would happen sooner in warmer ambient temps.

Damn sure not no plane mechanic, but it wouldn't be possible that someone ignored an FAA AD requiring fan replacement before 2020? Just a quick google on that engine series brought up a half dozen AD's on it.

Phil

Maybe swap sensors between engines and give it a run?

Bleed air is basically exhaust gas, right? I've had a 65 year career as a master auto mechanic, and 30+ years as an instructor- - - -little or no jet engine skills. Automotive engines have horrendous corrosion and carbon billdup problems with exhaust gas recirculation systems. Could you be dealing with some kind of similar problems with the bleed air system?

No. Bleed air is usually taken off of the N1 compressor, around 500°f and 40psi...

You need to forget about the chain of command for a sec and go straight to Honeywell.

Refuse to fly it until its fixed.There are always other jobs available.