Jump to content

starting TIT


rsd653
 Share

Recommended Posts

On behalf of rsd653 I m replying all the ques u asked. We r still facing the same problem.

starter control valve not opening fully, bleed air shut off valve not opening fully, starter

turbine damaged, compressor worn out/FOD'ed, cracked bleed air duct, blown bleed

duct gasket, speed sensitive valve porting air to bleed valves below 94%, TD amp

driving TD valve to PUT condition

starter control vale is ok, bleed air shut off valve operating good, starter turbine is ok, compressor checked, found ok. bleed air duck found in good condition, speed sensitive valve replaced with a new one,TD amp replaced with a new one. But still problem is there. I mean Start TIT is 856'C.

let us assume the starting time is ok!....props blade angle is in ground idle range ok...You've tried it in null!!........rigging is ok!!......could have to deal with an FCU change..What else could it be. ......................the bad John.......................................................I think if I recall.....had that kind of problem many sun arounds!!............Cheers to you guys!!

Yes starting time we get 45 sec to reach 60% for starting at first. prop angle at grd idle is 4'. yes we've tried in null. Rigging also correct. Yes we Have changed the FCU also. But still result was same.

I agree with NATOPS1 about the acceleration bleed valves. Disconnect the high pressure out line at the speed sensitive valve which goes to the acceleration bleed valves and see if it starts OK.

I had a bad speed sensitive valve one time which would close the valves at 45% and the TIT would increase rapidly. After shutdown a visual of the acceleration bleed valves revealed they were open because when the RPM droped below 45%.

We have changed the speed sensitive valve with a new serviceable one. But we've not tried the high pressure out line at speed sensitive valve. Tomorrow we are going to do that. The result we get, I'll let u know.

Well, lets see FCU change or something 100000000% easier... HUM.... There are so many things that can cause this, so to not do all the easy (cheaper) things first is not the best way to go about it.

It looks like rsd653 has done most of them so...

rsd653 when you say "Starting tit high more than 850'c" how high?

Have you tried to use high pressure air from an engine or just you GTC?

Pj brings up a good point the starter may turn the prop and engine but may bog down due to failure or the starter control valve may be "regulating" the air to the starter at a lower pressure.

When you start the engine how "low" does the air pressure go? At 16% what is the air pressure reading?

22 psi + I would guess as you continue the start until the overtemp.

What RPM do you get to befor the temp goes up? 30 40 or 60%?

We got some times 856, sometime 860'C also.

Yes we have tried high pr air also.

35psi+ with GTC.

we got 35% approx.

So friends, thanks all of u for all the replies u have given. We r really suffering a lot. Plz help us, how can we get rid of this high TIT prob. If u have any more queries plz ask. I'll answer as soon as possible. Our herculies is on ground for a long time. And we deadly want to see it air. Plz send your precious thinking and suggestions about the problem.

I m Waiting for your replies.

Link to comment
Share on other sites

An easy thing to do would be to shove a borescope into the left and right hand bleed collectors and inspect all of the 5th and 10th bleed valves all the way around. If you have one stuck in the closed position, that could easily cause your problem. So could indication problems between the thermocouples and the flight deck indicator.

The engine is obviously getting enough air since the engine winds up in 45 seconds. Unless fuel is being bypassed through the fuel enrichment valve, all other fuel causes should have been eliminated by now through changing all the components, including the TD system with starting in Null and changing the TD Valve.

At this point, you might as well flow test the fuel nozzles and check that the thermocouples haven't been burned up. Do all 4 engines read the same TIT after the aircraft has been shut down for 12 hours or more?

Link to comment
Share on other sites

Please "time" the engine from 0 to Maximum starter RPM (with the condition lever in GRND Stop)

Then "time" a good engine from 0 to Maximum starter RPM and post results.

Time from 0 to maximum ___________ sec.

Actual maximum RPM % ____________%.

This will tell me how your "air system" is operating...

Link to comment
Share on other sites

An easy thing to do would be to shove a borescope into the left and right hand bleed collectors and inspect all of the 5th and 10th bleed valves all the way around. If you have one stuck in the closed position, that could easily cause your problem. So could indication problems between the thermocouples and the flight deck indicator.

The engine is obviously getting enough air since the engine winds up in 45 seconds. Unless fuel is being bypassed through the fuel enrichment valve, all other fuel causes should have been eliminated by now through changing all the components, including the TD system with starting in Null and changing the TD Valve.

At this point, you might as well flow test the fuel nozzles and check that the thermocouples haven't been burned up. Do all 4 engines read the same TIT after the aircraft has been shut down for 12 hours or more?

Borescope test carr out, all the valves are ok. Indicators are good.

fuel enrichment valve has been changed with a new one. Prob still exists.

Fuel nozzles and thermocouples are also changed. No 2 eng (problem) shows less TIT than others.

Link to comment
Share on other sites

Time 45 with other eng, 65 with GTC.

Max RPM 22% with GTC. 32% without GTC.

These numbers are for the "good" engine or the "bad" engine?

I would like two sets of numbers...

Bad engine ... Time from 0 to Max RPM with GTC ____ sec...... and the Max RPM _____ % (also record the air pressure at 10%_____PSI).

Good eng ..... Time from 0 to Max RPM with GTC ____ sec...... and the Max RPM _____ % (also record the air pressure at 10%_____PSI).

OK I also noted the "shows less TIT than others" commet... Have you changed the "T" Block? (Junction of the Thermocouple harness and TD/Indicator leads?) Change this and see what the effect is you may have a resistance issue in the T block...

Link to comment
Share on other sites

Good day All of you!..........this snag has been on the board for at least a month!!!.....Doesn't make sense to me. This machine is not a toy!|.......Boroscope the mother or........get rid of it. Get it off the wing and operate!!! The thing is.....the Herc has to be functionnal!..... this bird has got to fly!!! Let somebody else take care of the engine!!............I rest my case mister the President!!!...........the bad John!!!

Link to comment
Share on other sites

  • 3 weeks later...

Hello, in the last week´s i have experiencied 2 problems like this, high tit. After doing some of the replacements that you describe, it all resume to cables that were wrong conected in the terminal block. The fact is that because of the cables were wrong conected, tha TD amplifier was reciving bad informatio. The way that we found it was puting a signal generator in the cables that go out of t block to the indicator in the cabin. We saw that the signal that we put wasn´t the one that the indicator show, the temp wasn´t good.

I hope that i can help. Sorry for my poor language.

:)

Link to comment
Share on other sites

Today is December 10th. The snag is still on the desk., You must have a spare engine somewhere !!. Take the engine OFF the wing!.......I just don't beleive it!!! Is anybody pulling our leg!!!!.......Sorry!!..I'm bad to the bone!!

We're gonna have to go down there boys and fix it!!........It reminds me the movie.....with Clint Eastwood.......goin' back in space. Come on guys over there.........rock and roll!! Fix it!!................oh well!!!

Link to comment
Share on other sites

  • 4 weeks later...

The speed sensitive valve can indeed cause a rapid rise in TIT during start. If the speed sensitive valve malfuntions in this manner it will partially cause the bleed valves to partially close creating a stall condition. In addition, the TD System can only take fuel during below 94% RPM.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...