Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
727 Compressor Stalls  
User currently offlineDrewwright From United States of America, joined May 2001, 621 posts, RR: 1
Posted (13 years 3 months 3 weeks 1 day 6 hours ago) and read 3609 times:

A couple of weeks ago I was watching a AA 727-200 runup for takeoff from MSY on the shorter runway, when it did it's typical howitzer bang/belch, out of the center engine. The pilot seemed to have a high RPM on the engine when it happened. He taxied off the runway and tried again a few minutes later. This time advanced the throttles more carefully. Again at a high RPM there was the Bang followed by a quick series of 8 to 10 bangs and a 20ft flame out the back of the engine. He then taxied back to the gate. A hour or so later he taxied out to the long runway and took off without incident. Why would he taxi back to the gate if compressor stalls are normal like this? There was a very light crosswind of about 5kts at the time, not really enough to induce that kind of stalling.

11 replies: All unread, jump to last
 
User currently offlineJT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3
Reply 1, posted (13 years 3 months 3 weeks 1 day 6 hours ago) and read 3530 times:

Compressor stalls are not normal on any engine. He went back to the gate, and Ill bet you money they found some kind of crud in one of the filters. Most common problem is a clogged drain orifice on the bottom of the fcu. As discussed in previous posts, the older P+W engines can take a lot of surging before something breaks. I saw a cf-6 come apart after one surge. Not trying to start that argument again though..JT


User currently offlineDrewwright From United States of America, joined May 2001, 621 posts, RR: 1
Reply 2, posted (13 years 3 months 3 weeks 1 day 6 hours ago) and read 3523 times:

I agree that the 727 engine is ultra tough and reliable, even now. Unlike the new engines today that even a minor hiccup results in a teardown. Working for Skywest I once witnessed a CF343 on one of our RJs blow parts out its tail pipe because of a bad airstart. Needless to say that engine was replaced.

User currently offlineJT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3
Reply 3, posted (13 years 3 months 3 weeks 1 day 5 hours ago) and read 3517 times:

We had a NG 737 lost about half the turbine do to what we think was flt crew error. He said he just added power to taxi away, and the engine shut down. He started the other engine, and taxied away. Then, for some unknown reason, he restarted the first engine without letting us look at it first. Thats when the real meltdown happened. the redline is 725. The eec showed a peak egt of 743, and above redline for 16 seconds. That will kill the strongest engine made. We found about a pound of metal on the ramp, after the initial failure. City ops found about twice that on the taxiway, where he restarted it. I have my theory on what happened, but I was watching MASH reruns in the breakroom, so I dont know for sure..JT

User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 4, posted (13 years 3 months 3 weeks 1 day 5 hours ago) and read 3520 times:

The 727 has an interstage bleed valve that sometimes sticks open.

The purpose of the interstage bleed valve is when the engine is running at idle the LP compressor sucks in more air than the HP compressor can use. The extra air needs to be bled off the compressor to avoid stalling.

If the interstage bleed valve fails to close when you run up the engine the engine will compressor stall.

Normal 727 operations require a 1.4 EPR check.

On takeoff with the brakes on you stand the thrust levers up to the 12 o'clock position. The engine will accelerate to approx 1.36 EPR. When the bleeds close the EPR will jump to 1.4 EPR. This is the only confirmation you will get that the bleeds have closed.

If the engineer who's job it it to call out "3 stable", or "bleeds closed" depending on company procedures calls them closed and they are not when you advance to TO power......BANG.

Then the CSD oil cooler switch, which bleeds air off the engines also, is placed to ground off and the EPR will jump again to 1.41 approx.

Failure of the interstage bleed valve is the most likely culprit for the #2 surge.

The JT8D engine is really bullet proof. You have to really do something wrong to damage it. The newer engines can't compare in durability.

JET


User currently offlineJT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3
Reply 5, posted (13 years 3 months 3 weeks 1 day 5 hours ago) and read 3511 times:

Im not sure what an interstage bleed valve is. Is it the same as prbc (pressure ratio bleed control). Ive just never heard that term before. The #2 engine doesnt have a 13th stage bleed, so Im confused. Can you explain?..JT

User currently offlineDrewwright From United States of America, joined May 2001, 621 posts, RR: 1
Reply 6, posted (13 years 3 months 3 weeks 1 day 5 hours ago) and read 3509 times:

Thanks JET, I figured that the engine was not damaged by the surging antics, just the pilots egos. I would have paid top dollar to be on that flight when the #2 rattled off like that, just to see the faces of the passengers. I suspect the F/A's had quite a few drink orders after the flight finally departed. BTW in my original posting I implied that the 727 compressor stall was common. I meant that only because, when working on the ramp etc, 99% of the time I have heard a compressor stall it has been from a 727. Although I have heard it on the 1011's too.

DRW


User currently offlineJT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3
Reply 7, posted (13 years 3 months 3 weeks 1 day 5 hours ago) and read 3510 times:

Ok, been thinking about pilots last post. I think you mean one of the 3 valves that let the air leak into the fan duct? Maybe I learned the wrong term, we call them the bleed control valves, or compressor bleed valves. We did not have the same experiance. Most of our probs were from a clogged filter, or the fcu water trap drain being clogged. A few times it was a stuck prbc, but almost never the valves I think you are describing..JT

User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 8, posted (13 years 3 months 3 weeks 1 day 3 hours ago) and read 3513 times:

No I am probably wrong in my terminology. I remember it being called the interstage bleed valve on one of the planes I flew either the DC8 with the JT3D, or the Beach 1900 with the PT6A-65B, or the 727 with the JT8D. All the info kinda blurs over the years. The closer you get to recurrent the more blured it is.

I just assumed it was called that on all engines and I'm probably wrong.

But the valve no matter what it's called does the same thing.

The valve does leak the excess air into the fan duct.

Maybe it won't cause surging as I described (I was told that in ground school) but the purpose for the 1.4 EPR check is to make sure those valves are closed.

When the valve does close in about 2 seconds after you stand the thrust levers up the needle swings to 1.4 EPR pretty quickly.

I've actually never had an experience on the 727 with a sticking valve. I have had a slow one where it takes longer than the rest to close and causes a slow EPR rise to 1.4.

The only problem I have ever had with compressor stalling, even on the 100 series with the original oval duct (much better looking than the round one in my opinion) is when holding #2 in reverse too long when slowing down. It will begin compresor stalling at about 50 knots in reverse detent.

In an empty freighter, with the sound proofing removed to save weight, it will get your attention.

JET


User currently offlineJT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3
Reply 9, posted (13 years 3 months 3 weeks 23 hours ago) and read 3486 times:

This business will cause "memory decay" wont it? Whatever terms we use, we are talking about the same valve. The check you use to verify valve position seems to be a good idea. You should see the maint manual version of it. What you guys do in 15 seconds, takes us 15 mins. Thanks for your response, info and humor, good combination..JT

User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 34
Reply 10, posted (13 years 3 months 3 weeks 10 hours ago) and read 3479 times:

If the 13th stage compressor bleed valve stuck "open", the most likely outcome wouldn't be a stall but the EGT reaching its limit before attaining T/O EPR. If the bleed valves closed too early, this would likely cause a stall, amongst other things.

The JT8 seems to have more combinations of internal bleed valves than Carter has liver pills. If I remember correctly they reduced the amount of 13th stage bleed valves for more 8th stage ones to increase fuel efficiency. Plus the start bleed system to unload the compressor during start.



You're only as good as your last departure.
User currently offlineJT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3
Reply 11, posted (13 years 3 months 3 weeks 8 hours ago) and read 3465 times:

FDX, there were a bunch of models, but the start bleed valve was added on the -200 series engines. I dont know if they started on the old models, but I know all the -200 have it. None of our older engines had that system. If you have seen the older ones with the start bleed valve, let me know. My instructors told me it didnt exist, maybe a rude E-mail to the training department is in order?--lol..JT

Top Of Page
Forum Index

Reply To This Topic 727 Compressor Stalls
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Compressor Stalls? posted Mon Apr 26 2004 00:26:51 by Aloges
Info On 707 Testing 727 Engines posted Wed Dec 6 2006 16:39:20 by Nosedive
Compressor / Turbine Disc Cross Sectional Shape. posted Sun Nov 5 2006 09:39:48 by JetMech
Why JT8-D For 727 Insteed Of TF30 posted Fri Sep 8 2006 19:35:00 by 747400sp
Why No Douglas Competitor To The Boeing 727? posted Mon Jul 31 2006 21:51:50 by 747400sp
UK Current 727 Operators posted Sat Jul 8 2006 02:05:24 by RichM
787 Electric-Compressor Pressurization posted Wed Jun 7 2006 18:48:41 by Redcordes
Transmile 727 Incident, 04May06 posted Thu Jun 1 2006 06:25:56 by N685FE
A 727 Lonely Pilot posted Wed May 31 2006 08:09:17 by AR385
Why Has The 727 Lost Cruising Speed? posted Fri May 26 2006 18:39:41 by 747400sp
Compressor Stalls? posted Mon Apr 26 2004 00:26:51 by Aloges
CO 727 Take Off Video,whats Happening? posted Sat Jan 21 2012 10:44:10 by readytotaxi
727-200 & 737-200 "Advanced". What Made Them So? posted Mon Dec 19 2011 19:23:30 by lat41
A Puff Of Smoke From The Wing Of A 727? posted Thu Nov 24 2011 01:13:13 by B737-112
Did Fedex Retire Some 727's Recently? posted Tue Nov 8 2011 19:06:47 by lexkid12300
707/727 Ground Service Question(s) posted Tue Jul 26 2011 19:10:55 by SXDFC
Air Hong Kong 727 Callsign posted Fri Jul 1 2011 01:26:55 by QF108
727 Question? posted Wed Jun 8 2011 13:42:58 by b767
727 Engineer Panel Questions posted Thu May 5 2011 15:11:28 by FlyMKG
Timing Of 727-200 Pure Freighter posted Wed Mar 2 2011 19:32:02 by Newark727

Sponsor Message:
Printer friendly format