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.

I met a former Lear engineer who presented at the IA seminar a couple years who might help. Will look for info and pm if I find him.

Thank you all, I am following all responses and I am appreciative of all of them.

Just to clarify, I am 100% confident there is no bleed air leak. After several through extensive inspections, nothing is burning in there.

The red EICAS message can’t be ignored. The checklist to make the light extinguish is followed and the flight can be completed as planned.

I will follow the advise given. If it is some sort of AV glitch, I want it fixed. Damn computers!

Thanks again to everybody.

Try contacting these people. They know Lear jets.

https://airaffairs.com.au/

Remember the good old days when all you had to worry about was a fire warning light in the engine "T" handle...

Don't get me started on fire warning faults and T Handles....

FL420 is way up there a cracked exhaust flange might give a fault up high and be hard to find on the ground. I assume the mechanics used soapy water on a running engine before they said there were no leaks.

Some aircraft, Piper Cheyenne III comes to mind can have a bleed air leak with no indication.

When you pull the power back you are reseting something. As someone said earlier these is a PC board somewhere with corrosion on the puns or a leaky diode or a faulty transistor.

You need to isolate the airframe and engine seals and tubing first as that is the easiest

As you know a bleed air leak can cause a lot of damage in a hurry.

Fire loops can be such a pia to troubleshoot at times but it's possible that the connector that leads up to the loop is breaking down when it gets warm. I'm not so sure it's an avionics issue since it turns off when you shut off the rt bleed air and idle back the engine, has it been checked on a ground run or is that even possible? I've only ever worked on heavies so I'm not schooled up on these particular airframes.

Is there a change in the pressurization or air conditioning schedule at around 40,000’ ?

Talking about this over coffee with ATP pulled up.
A friend said he has seen insulators on the fire loop ground out an hour into flight . Airflow, pressure and temperature change caused it.

Some baling wire and duct tape and you'll be good to go.

Does it happen if you level off below FL430????

I can't believe ALL your flights you go to 43.....

Can't really believe that with both warnings in RED and on multiple occasions that the plane hasn't been grounded, if not by the owner, then by the pilot...

Phil

Is this aircraft an LJ-31A?

My BIL spent 23 years in the AF as a jet engine mechanic, got out and did 20 something with Honeywell. Anyway this is what he says. Probably a bad over temperature sending unit...seen this before when I was in the AF. That's a pathetic A&P mechanic if he can't figure that out. They will get a computer disagree code for it eventually. Mechanics these days don't know how to troubleshoot a problem, they need a computer to diagnose for them.

My brother’s an A&P.

Get a new A&P.

Ask your A&P to clean the computer ground connections at the airframe and the terminals. It is amazing that how many glitches like this are caused by nothing more than a poor ground connection.

drover

This sounds likely. I have a bit of GE and Allison experience, and bleed air isn't an uncommon problem. The fact that it comes in after leveling off is key. Could be temperature related, and could be the harness is being affected by the change in flaps. Chase grounds, cannon plugs, and the sensor first.

Is it calculated or measured?

I still don't know whether this is a 31A or not, but if it is there are two temp sensors associated with bleed air: one for the bleed air duct and one that senses temps in the pylon. When you say "fire loop," I think of the fire loops inside the engine nacelles for detecting engine fires. I would imagine that this is a common configuration on the Lear business jets (admittedly a shot-in-the-dark guess).

This is the obvious answer. Also, I wouldn't run it with the red light on. It ain't rocket science.

Yes. Bleed air comes off before combustion.

No, not all flight are to 410 or 430, but I’ve never had it happen yet at 430-450. Yesterday it didn’t happen at all and I flew for 3 hours above 400. If I stay below say, somewhere around 320, I haven’t seen it. It seems to happen right around the 400 level.

Well... did your mech get to the bottom of the gripe?