Delta MD-88 Compressor Stall In Flight

laurco · Fri Oct 07, 2011 3:45 pm

I have some questions about an experience on a flight a couple days ago. As a frequent business traveler it was unsettling but also I am curious about what happened and perspectives of the experts here.

30 minutes into the flight we heard a loud bang on an MD-88. The airplane appeared to be flying normally before and after the noise. The pilot came on 5-10 minutes later to report a compressor stall on the right engine (like a backfire), that it occured while we were passing through 26,000 feet, and that the engine was still running. Weather was clear. He said they were going through their checklists but likely would have to return back to ATL. He came back on about 5-10 mins later to say after consulting with ops they were going to return to ATL, that the engine was running at reduced rates. In the return to ATL it seemed like banking was more gradual. We also flew closer than normal to the city and a shorter final approach understandable. It did seem like we kind of floated in more than usual but had a normal landing. After landing the pilot said they had shut down the engine totally before landing. Of course great job by the pilots.

So my questions are:

1. Any idea what may have happened or possible causes?
2. Is this a common occurence?
3. Was it dangerous?
4. Is there any sort of incident reporting required, so I can track what happened?

Thanks for any insights.

shufflemoomin · Fri Oct 07, 2011 4:16 pm

I think you're more likely to get better responses if you post this in tech/ops.

seabosdca · Fri Oct 07, 2011 4:35 pm

Quoting laurco (Thread starter):
1. Any idea what may have happened or possible causes?

Sudden windshear or other disturbance in the air coming into the engine, or maybe an exceptionally high-flying bird (they occasionally do get that high).

Quoting laurco (Thread starter):
2. Is this a common occurence?

Relatively, although it happens more often on takeoff and initial climb.

Quoting laurco (Thread starter):
3. Was it dangerous?

Would I rather have two correctly working engines? Yes, of course. Was it "dangerous?" Probably not. I can't think of a crash caused by a compressor stall without another failure of some sort involved.

airbuseric · Fri Oct 07, 2011 4:54 pm

Welcome to a.net

Quoting laurco (Thread starter):
Was it dangerous?

No, the aircraft is capable to operate on one engine as well, and the flightcrew is trained to operate the aircraft safely under such conditions.

Quoting laurco (Thread starter):
Is there any sort of incident reporting required, so I can track what happened?

At least internally an incident report and captains report will be made about this happening. Of course the airline will try to trace back what made this occurance happen to the engine. A public report is not likely to show up for these cases.

lowrider · Fri Oct 07, 2011 7:24 pm

Quoting laurco (Thread starter):
1. Any idea what may have happened or possible causes?

A compressor stall can be caused by a wide variety of issues, the below gives a nice overview
http://en.wikipedia.org/wiki/Compressor_stall

Quoting laurco (Thread starter):
2. Is this a common occurence?

I would say it depends on where you fly and what sort of aircraft, but generally speaking, no.

Quoting laurco (Thread starter):
3. Was it dangerous?

As others have indicated, it is a matter of degree. It was dangerous enough that the crew returned to Atlanta rather than continue, but death or serious injury was probably not likely or imminent.

Quoting laurco (Thread starter):
4. Is there any sort of incident reporting required, so I can track what happened?

Unless you have some contacts inside the Delta maintenance department, no.

roguetrader · Fri Oct 07, 2011 8:11 pm

Back in the 727 heyday this happened quite a bit to me - 4 or 5 times over 10 or 12 years from the 70s to 80s. Always at DFW or ATL. The S intake on the #2 engine, I was told, was especially likely to suffer a compressor stall in crosswind conditions. I had it happen mostly at takeoff but once also on landing and one even while merely during taxi to the gate. It makes a hell of a noise and your immediate thought is "Sh*t, something on the plane just exploded, prepare for death!"...but the pilots were uniformly calm about it and a few times took the time to explain it in detail. I remember hearing that there was a slight chance the fan blades could get bent during a compressor stall, which was the main reason to turn back and grab a new airplane (or at least have the blades inspected).

I think something about tail-mounted engines also makes them more susceptible to this?

All in all not too much of a true danger but plenty of a scare....lots more drinking on the eventual re-initiated flight (by the pax - probably not by the crew...)

RT

MarkC · Sat Oct 08, 2011 12:25 am

Quoting lowrider (Reply 4):
Unless you have some contacts inside the Delta maintenance department, no.

Some of us do.

But, hey, JT8 compressor stalls are not exactly a rarity.

JETPILOT · Sat Oct 08, 2011 12:55 am

The JT8D is pretty much immune from damage from compressor stalls. It's bullet proof. No true about engines with variable compressor blades. I never had an issue with a JT8D after compressor stalling. We would check the engine parameters and if all was well keep going.

One takeoff in the 727 we would stand the throttles to 1.4 EPR and make sure the interstage bleed valves would close before going to takeoff power. If the IBV didn't close then you would get a compressor stall on TO. The FE would call out "1.4 EPR, bleeds closed, auto pack trip armed, takeoff checklist complete".

The DC8 with the JT3D had the same compressor stall issues but were also bulletproof.

Yukon880 · Sat Oct 08, 2011 1:47 am

Echoed sentiments for the JT3D and JT8Ds...
Once upon a time, Pratt & Whitney and "bulletproof" were near constant companions!

mrskyguy · Sat Oct 08, 2011 4:12 pm

Quoting jetpilot (Reply 7):
One takeoff in the 727 we would stand the throttles to 1.4 EPR and make sure the interstage bleed valves would close before going to takeoff power. If the IBV didn't close then you would get a compressor stall on TO. The FE would call out "1.4 EPR, bleeds closed, auto pack trip armed, takeoff checklist complete".

That's very interesting. How much was the incidence of compressor stall occurrences reduced if this procedure was followed?

JETPILOT · Sat Oct 08, 2011 6:26 pm

Quoting mrskyguy (Reply 9):
That's very interesting. How much was the incidence of compressor stall occurrences reduced if this procedure was followed?

When you pushed the throttles up to 1.4 EPR the throttles would stabilize there and then there would be a small jump and increase of the EPR when the interstasge bleed valve closed. The IBV was a valve in between the low and high pressure compressor that bled off air from the low pressure compressor because at low power settings the HPC couldn't use the volume produced by the LPC. If the IBV closed as it should then the occurence would be 0 unless it was caused by some other factor like a crosswind.

I have over 3500 hours in the 727 and have only had one compressor stall when landing. #2 in reverse stalled. It didn't happen often. The #2 air inlet duct was changed on the -200 series to a round duct from the original oval duct on the -100 to prevent compressor stalling. In a stiff crosswind I would bring #2 up to TO power only after reaching 20kts. That's not a Boeing or company procedure. Just something I had passed on to me from other 727 pilots.

my235 · Sat Oct 08, 2011 6:56 pm

Quoting shufflemoomin (Reply 1):
I think you're more likely to get better responses if you post this in tech/ops.

Uhhhhh....This is the Tech/Ops.

Starlionblue · Sat Oct 08, 2011 10:39 pm

Quoting my235 (Reply 11):
Quoting shufflemoomin (Reply 1):
I think you're more likely to get better responses if you post this in tech/ops.

Uhhhhh....This is the Tech/Ops.

The thread was most likely moved here.

[Edited 2011-10-08 15:39:50]

BMI727 · Sat Oct 08, 2011 11:31 pm

Quoting laurco (Thread starter):
2. Is this a common occurence?

Relatively, yes. It rarely causes any major damage or danger and is just an inconvenience. 26,000 is high if it was a bird, but it is far from unheard of for some large birds (Canadian geese come to mind) to get that high or higher.

Quoting laurco (Thread starter):
4. Is there any sort of incident reporting required, so I can track what happened?

Not likely. Probably the mechanics will go over the engine (and other parts of the aircraft if a bird strike is suspected) and put it right back on the line.

Quoting roguetrader (Reply 5):
I think something about tail-mounted engines also makes them more susceptible to this?

Perhaps the possibility of being exposed to "dirty" air from the wings and fuselage makes them more susceptible. But on the other hand, tail mounted engines are less likely to suffer FOD damage.

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