# Do airline SOP normally recommend an in-flight engine restart in the case of an unexplained shutdown?

You're flying along at cruise in say a 737 or similar twin-engined yet. Suddenly, one of your engines shut down for no apparent reason. (or no abnormal indications such as low oil or similar)

Do you:

• Attempt a restart and either divert or continue?
• Divert and leave it off for an emergency landing?
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depends on the malfunction – ratchet freak Jun 9 '14 at 14:39
I'd also be curious to see a checklist, but I'd have to assume that if the shut down was entirely unexplained and random you'd have to try and restart it. The first step in an unexplained situation is to diagnose the problem (if the craft is reasonably stable). And trying a restart would be a good way to get a diagnoses. On top of all that, I've read several transcripts where the pilot loses an engine and immediately tries to restart it... I just don't have a checklist to prove it or I'd make this an answer... – Jay Carr Jun 9 '14 at 14:43

According to item 6-14 in the 737NG Abnormal Procedures Handbook, you're basically supposed to make sure that the engine is shut down completely and then divert to the nearest suitable airport.

From The 737NG Abnormal Procedures Handbook

ENGINE FAILURE/SHUTDOWN
Condition: Loss of all thrust on an engine accompanied by illumination of the ENG FAIL alert or abnormal engine indications
Accomplish an engine shutdown only when flight conditions permit.

• AUTOTHROTTLE (if engaged): DISENGAGE
• THRUST LEVER (affected engine): IDLE
• ENGINE START LEVER: CUTOFF
• APU (if available): START & ON
• BUS PACK SWITCH (affected side): OFF
• FUEL: BALANCE

If wing anti-ice is required:
- ISOLATION VALVE SWITCH: AUTO

Plan to land at the nearest suitable airport. ACCOMPLISH ONE ENGINE INOPERATIVE LANDING CHECKLIST (BELOW)

So, if we're going by the book, I think that diverting would be SOP.

That being said, I've read of several examples (like TACA Flight 110 and Flight BD 092) where the crew tried their best to restart the engine when one or both of the engines flamed out. So, while the book suggests just shutting the engine down and working on diverting, it seems the common practice is to work on diverting while also trying to start the engine again.

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Your question mentions the 737 or similar. If you want answers limited to 2-engine jets, let me know and I'll remove this answer as it is for the 747-100 or -200.

Whether to restart or not depends on the nature of the failure. If there appears to be no problem to do otherwise, a restart would be in order. The checklist for an inflight start from the last airline I flew for (now out of business) is below. The code to the right of each action is who performs it: C - captain, FE - flight engineer, All - all 3 crew members.

Thurst Lever ............................... CLOSE        C

Start Lever ................................ CUTOFF       C

Fuel Pressure .............................. AVAILABLE    FE

Bleed Air Valve ............................ OPEN         FE

Engine Ignition (Sys 1 and Sys 2)

Above 250 KTS ......................... FLT START    FE

250 KTS and Below ..................... GND START    FE

Start Lever ................................ RICH/IDLE    C

Engine Instruments ......................... STABILIZED   ALL

Start Lever ................................ IDLE         C

Engine Ignition ............................ AS REQUIRED  FE

Electrical Power ........................... RESTORE      FE


The most likely cause for a Pratt & Whitney JT-9 engine to quit is poor technique on the part of the pilot. If you're at altitude and starting the initial descent, you should put the nose down before bringing the thrust levers back. Also, don't slam them back, take a few seconds to do it, especially if you're above FL370.

It's worth noting that on the 747, the loss of an engine (no restart) enroute is not considered a serious emergency. At the two 747 carriers I flew for, it was the captain's discretion as to whether to divert or to continue on.

Also, it's not always the case of either the engine works at the power of the other engines or it doesn't. There are situations where the engine might be available, but with partial power. As I remember there were at least two such cases, one of which was high oil temperature. Basically the work-around was to run the engine at that power setting that would keep the oil temp below the maximum.

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Thanks Terry :) very interesting although I suspect that as perhaps the engine reliability is higher today and with funky stuff like FADEC, the operational philosophy on new aircraft has changed since failures of the types you mention are much less common? – MikeFoxtrot Jun 9 '14 at 17:42
@MikeFoxtrot I suspect you are correct on both counts. I always wonder whether I should contribute from experience that is now so out of date. Sometimes I choose not to, other times to go ahead if I think there is some worth in knowing what it used to be, only if to make the current generation appreciate what they now have operationally. Reminds me somewhat of listening to old pilots when I was a kid in the 1950s. There were those who actually believed in the old cliche that all the fun had gone out of flying when they covered cockpits. BTW, the 2 planes used for Air Force One are 747-200s – Terry Jun 10 '14 at 0:32
This is not that out of date. In 2005, a BA 747-436 from LAX bound to Heathrow suffered engine failure, but rather than turn around and land, the crew decided to proceed. The incident report has more. – Burhan Khalid Jun 10 '14 at 12:30