Many here would be aware of the Qantas B737-838 that declared a Mayday over the Tasman Sea after it's #1 engine failed, Mayday was later reduced to Pan-Pan and A/C landed safely.
On landing the pilot deployed the thrust reversers on both engines and there appeared to be very little rudder deflection.
Do those actions imply that the crew may have managed to restart the engine prior to landing?

IDLE reverse on the operating engine wouldn’t produce much yaw, even something above idle.

If the reverser on the failed engine opened then the engine was running. IIRC if the engine is INOP you can’t get the reverse selector out of the interlock and it won’t deploy. I’ve been off the 737 for a while though so take that with a grain of salt.

It is possible they didn't actually shut it right down but just idled it.

My non-pilot understanding - and hopefully someone would correct me if I am wrong - a first step to handle an engine problem is to reduce power to idle. It still triggers diversion requirement (although not as strict as full shutdown) under the assumption that a problematic engine could still run for some time at real power if things go VERY wrong and another engine fails as well.
Such rollback is often reported as shutdown - although actual IFSD is an escalation of the situation.

kalvado wrote:

My non-pilot understanding - and hopefully someone would correct me if I am wrong - a first step to handle an engine problem is to reduce power to idle. It still triggers diversion requirement (although not as strict as full shutdown) under the assumption that a problematic engine could still run for some time at real power if things go VERY wrong and another engine fails as well.
Such rollback is often reported as shutdown - although actual IFSD is an escalation of the situation.

It depends on the nature of the issue, but yes, some out of band indications might initially require reducing affected engine to idle and perform some checklist items. If it was a major failure like a blade-off event it would generally be shut down completely. Passengers reported a bang, which could be a compressor stall, although not common at cruising altitude and power settings.

Reducing to idle is better than a full shutdown, but only just - while you retain elec/hyd/air (depending on whats happened) you don't really get meaningful thrust and so the plane is effectively on one engine from a thrust point of view. Not an issue on descent but with an hour or two to fly its obviously an issue..

There are many reasons to shut an engine down. High oil temp, low oil press, high vibration and obviously fire etc. Many of these cases can be solved by simply reducing the thrust. This is particularly true for high vibration, high oil temp or high EGT. By reducing the thrust, but not shutting the engine down, you get to keep the auxiliary systems like the electrical generator and bleed. These system are quite important when you are operating in remote areas like these guys were.

Of less importance is the company engine shutdown statistics. An unnecessary engine shutdown would have a negative impact on those stats and it could effects EDTO maintenance compliance.

Stealthz wrote:

Many here would be aware of the Qantas B737-838 that declared a Mayday over the Tasman Sea after it's #1 engine failed, Mayday was later reduced to Pan-Pan and A/C landed safely.
On landing the pilot deployed the thrust reversers on both engines and there appeared to be very little rudder deflection.
Do those actions imply that the crew may have managed to restart the engine prior to landing?

They probably just went to reverse idle. When I flew the 737 that’s all I did in sim-world for practicing single engine landings. Anything more and you’re dealing with asymmetric thrust and risk starting a rudder dance on rollout. If you’re using autobrakes, there’s no stopping benefit of using more reverse thrust, it’s all the same deceleration rate, just takes the burden off the brakes. I’d never go above reverse idle while single engine, or with a T/R inop. Too much compensation and brain power needed!

As others have pointed out the TR on a 737 will not deploy if the engine has been shut down. Especially since the crew reduced their status to a Pan Pan it would suggest that either:

1. The engine simply flamed out with no apparent damage and they were able to restart it, or
2. The engine was never actually shut down but simply reduced to idle in order to address some relatively minor issue or parameter that was out of limitation (oil temp, compressor stall, etc.)

In any case when landing single engine we generally don't use more than idle reverse to avoid the issue of asymmetric (reverse) thrust. When I flew the -200 this was a problem even on normal landings as the engines would often spool up at different rates.

FWIW, our procedure is to pull both reversers if at least one engine or reverser is working. For example, if one reverser is MELed we'd still pull both. We'd only not pull reverse if both were inop.

This prevents us from pulling the wrong one with an engine or reverser inop.If you pull both, you'll get all the reverse you can get in that situation, and pulling the inop one doesn't make a difference.

Starlionblue wrote:

FWIW, our procedure is to pull both reversers if at least one engine or reverser is working. For example, if one reverser is MELed we'd still pull both. We'd only not pull reverse if both were inop.

This prevents us from pulling the wrong one with an engine or reverser inop.If you pull both, you'll get all the reverse you can get in that situation, and pulling the inop one doesn't make a difference.

On the 737 the reverse lever will not move beyond a certain point until it fully deploys (which obviously it never will if an engine is inop) and I have seen crews struggle with this in the sim during SE ops, so we train to only pull the reverser on the operating engine. I definitely see the merit in your procedure though.

On a related note, I never understood why (on aircraft with a separate fuel cutoff switch/lever) we don't use both (all) of the thrust levers together following an engine failure. It wasn't possible on the CRJ since the thrust lever itself had a "cutoff" detent, but on the 737 once you cut the fuel the thrust lever on the dead engine isn't doing anything. The C-5 crash in Dover likely would not have happened if the crew simply used all 4 thrust levers following the engine failure.

ArcticFlyer wrote:

Starlionblue wrote:

FWIW, our procedure is to pull both reversers if at least one engine or reverser is working. For example, if one reverser is MELed we'd still pull both. We'd only not pull reverse if both were inop.

This prevents us from pulling the wrong one with an engine or reverser inop.If you pull both, you'll get all the reverse you can get in that situation, and pulling the inop one doesn't make a difference.

On the 737 the reverse lever will not move beyond a certain point until it fully deploys (which obviously it never will if an engine is inop) and I have seen crews struggle with this in the sim during SE ops, so we train to only pull the reverser on the operating engine. I definitely see the merit in your procedure though.

On a related note, I never understood why (on aircraft with a separate fuel cutoff switch/lever) we don't use both (all) of the thrust levers together following an engine failure. It wasn't possible on the CRJ since the thrust lever itself had a "cutoff" detent, but on the 737 once you cut the fuel the thrust lever on the dead engine isn't doing anything. The C-5 crash in Dover likely would not have happened if the crew simply used all 4 thrust levers following the engine failure.

I wonder if that is a factor in the new single lever Falcon?

ArcticFlyer wrote:

As others have pointed out the TR on a 737 will not deploy if the engine has been shut down. Especially since the crew reduced their status to a Pan Pan it would suggest that either:

1. The engine simply flamed out with no apparent damage and they were able to restart it, or
2. The engine was never actually shut down but simply reduced to idle in order to address some relatively minor issue or parameter that was out of limitation (oil temp, compressor stall, etc.)

In any case when landing single engine we generally don't use more than idle reverse to avoid the issue of asymmetric (reverse) thrust. When I flew the -200 this was a problem even on normal landings as the engines would often spool up at different rates.

Can you explain the 737 systems to me please ?

When troubleshooting reverser issues at the gate on the aircraft I fly, we can deploy the "reverser" (which is nothing more than a hydraulically actuated translating sleeve) without the engine running. All it requires on the type I fly is hydraulic power, and the safety interlocks logic met (if the fire shutoff is used, the hydraulics are inhibited in the pylon).

zeke wrote:

Can you explain the 737 systems to me please ?

When troubleshooting reverser issues at the gate on the aircraft I fly, we can deploy the "reverser" (which is nothing more than a hydraulically actuated translating sleeve) without the engine running. All it requires on the type I fly is hydraulic power, and the safety interlocks logic met (if the fire shutoff is used, the hydraulics are inhibited in the pylon).

We can do (and I have done) the exact same thing on the 737. As long as the hydraulics are pressurized you can cycle the reverser all day long whether the engine is running or not. However, when an engine fails in flight part of the procedure is to pull the fire switch (whether or not there is a fire indication) and that action, among other things, locks out the associated TR.

ArcticFlyer wrote:

zeke wrote:

We can do (and I have done) the exact same thing on the 737. As long as the hydraulics are pressurized you can cycle the reverser all day long whether the engine is running or not. However, when an engine fails in flight part of the procedure is to pull the fire switch (whether or not there is a fire indication) and that action, among other things, locks out the associated TR.

On other aircraft types, the fire handle/switch/button s exercised only if there is damage or a fire.

It is not used on a shutdown, as you might want to try and restart it.

zeke wrote:

ArcticFlyer wrote:

We can do (and I have done) the exact same thing on the 737. As long as the hydraulics are pressurized you can cycle the reverser all day long whether the engine is running or not. However, when an engine fails in flight part of the procedure is to pull the fire switch (whether or not there is a fire indication) and that action, among other things, locks out the associated TR.

On other aircraft types, the fire handle/switch/button s exercised only if there is damage or a fire.

It is not used on a shutdown, as you might want to try and restart it.

You are correct - as a sim instructor we only ever do fire/severe damage so that's the procedure that came to mind. I had to check but the separate (non-memory) procedure for an engine flameout or shutdown, with no indication of fire or damage, does not call for the fire switch to be pulled.