Go around

[limpitakis]

Hello to all,
Having seen a documentary regarding the AM 3054 Crash in Brazil I would like you to help me understand the following warning from airbus,

The pilots tried to execute a 'go-around' or re-take-off – which Airbus strongly warns pilots not to do in this situation because the mechanics of re-reversing the fully functional engine could cause a stall,

My question is why the re-reversing of a fu;;y functional engine could cause a stall?

Thank you,
Nick

[framer]

They are not talking about an aerodynamic stall of the wings but an aerodynamic stall of the engine. ie a disruption, potentially even a reversal, of airflow within the engine.

[limpitakis]

Thank you for your reply,
I was referring to the engine stall as well,
I need to understand why re enabling full thrust after a reverse (re-reverse) could cause an engine stall,
Would it be more gentle to go to idle first and then apply full thrust? What would be the air flow dynamics inside the engine then?
Nick

[hetfield]

limpitakis,

the idea, not to select fwd thrust out of an engine which is in reverse is precautionary.

It may work, but, many mechanical, electronic, bleed or hyd parts/linkages are in the reverse logic/mechanism.

One or some may fail..... in a situation where you need fwd thrust.

[grounded27]

Would it be more gentle to go to idle first and then apply full thrust? What would be the air flow dynamics inside the engine then?
Nick

Your engine is going to transition from reverse thrust to (seek) idle as you drop the levers then seek thrust settings. The engine spooling up or down as fwd thrust or reverse thrust is selected is the largest factor as I see it.

The reverser's move faster than the engine can spool up or down. Gentle is beyond your control when in this condition, going to idle will do little when faced with a go-around, rock and a hard place. Down to the PIC decision to over run aground or take a chance on an engine surge. Speed, Rwy length, Rwy performance, sounds like Airbus made a statement to reduce their liability in a situation where a (wheels on ground) go around W/O reverse thrust should have been made.

[italia458]

I was told by an ex-Captain and Check pilot for the A330/A340 that the SOP at his airline was that no go around was to be initiated after reverse thrust had been selected. He said it had to do with the manufacturer not being able to guarantee that the reverse thrust doors will close.

Pacific Western Airlines Flight 314 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Pacific_Western_Airlines_Flight_314)

[limpitakis]

Thank you too for your reply,
Of course the engine is going to transition from reverse thrust to idle as Idrop the levers then seek thrust settings. What I ment and mentioned was the word gently in other words to give the engine a chance to recover from reverse to idle rather than apply immediately full thrust even though time is crucial for a go around especially in short runways, rainy conditions, remaining runway , e.t.c
Thank you again for your input,
Just out of curiosity is there any similar instruction(s) from Boeing or is it Airbus too cautious alerting pilots not to attempt the specific action?
Thank you all,
Nick

[Slasher]

Boeing notice I recall was that you don't attempt a go around
(wave off) if reverse is already selected. You can wave off as
long as the buckets are fully stowed. As italia458 has said the
buckets might not close together simultaneously or one could
hang up.

As for the airboos suck-squirt I've always followed the same
rule.

[Capt Claret]

The following warning is a cut 'n paste from the Douglas/Boeing 717 FCOM.

WARNING: If touchdown occurs and reverse thrust is initiated, a full stop landing must be made.

[limpitakis]

Thank you all for your replies,
Quite clear now.
Nick

[The Real Pink Baron]

The engine does not reverse direction!! Only the buckets come out and deflect the thrust in an almost forward direction. The engine is still turning the same way.

[grounded27]

What I ment and mentioned was the word gently in other words to give the engine a chance to recover from reverse to idle rather than apply immediately full thrust even though time is crucial for a go around especially in short runways, rainy conditions, remaining runway , e.t.c
Thank you again for your input,


What you seem to fail to understand is that it does not matter, as you stow the reversers engine will seek idle, it may not spool all the way down but if you can see the fence at the end of the RWY and wish to fly over it as opposed to drive through it firewall them!

[framer]

The engine does not reverse direction!!

I don't think anyone is suggesting it does. Were you lead to that conclusion by my comments about airflow reversal and stalls?

[john_tullamarine]

With older technology engines, especially, reversers hanging up when commanded to restow in a dynamic situation were a real hardware concern.

Hence the admonition - reversers out, aircraft stopping.

Can recall this being a contentious issue at the enquiry into the Sydney crash of VH-AAV in 1980. An AN B727, landing at the time, had conflicting ATC instructions (as I recall) and, once the buckets were out, the Captain (BG) declined further instructions to go around.

The reality is that it takes some time to get the reversers stowed and the luxury of contemplative time is one commodity the pilot doesn't have in the situation where he/she is contemplating a go around from the initial touchdown.

[Capt Claret]

Were I a betting man, I'd say the prohibition, or advice, not to initiate a go around once the reversers have been selected is as much to do with human factors as with engine management.

Lots of runway can be used stowing reversers and then selecting TOGA power, if on a shortish runway grief could be the result. On a long runway, one would probably get away with it.

By prohibiting the practice, it avoids the last minute "it seemed like a good idea at the time" decision.