View Full Version : TOGA or FLEX if Engine Fails at V1?(A320)

4th Apr 2009, 13:54
Hello friends, this is my first contribution to this great forum.
I was wondering which is better: to use TOGA or continue with FLEX if Engine Fails at V1, some fox say that if the weight is light you may continue with FLEX and if heavy consider TOGA, but the SOP of Airbus says the following:


TOGA requires more rudder input.Note:

Setting TOGA, when out of SRS mode with slats extended, triggers go-around mode.
TOGA is not allowed in case of derated T.O on ground.
Just need some comments from pilots

4th Apr 2009, 14:29
If your performance department has done its homework, there will not be obstacle clearance issue with flex. Also there will be no controlabillity issue with TOGA. More rudder is needed but if you respect v1 and v2 limited by VMCG/A, there's no chance of running out of rudder.

Airbus got it right.

The answer is: whatever.

4th Apr 2009, 20:15
By definition, maintaining Flex is "sufficient power" to climb away... However, that might require a high degree of flying accuracy, with any degradation leading to unsatisfactory airspeed / RoC.

That said, selecting TOGA from a stable climb out will destablise the situation somewhat... :ooh:

Personally, I will leave Flex, and see how it goes. If either I or my colleague (I brief the P2 to feel free to state/call TOGA) are unhappy with the perforrmance, I will then go for TOGA.

In a lightweight / high V speeds situation, keeping Flex slows everything down nicely ;)


5th Apr 2009, 04:43
From my experience of V1 cuts in the sim at heavy weight, I would always use TOGA (from a Flex take-off, not a Derated take-off). Even if the climb performance has been calculated to be sufficient, doesn't make much sense to use less than TOGA when half the thurst is gone and the drag has increased. Wait until the gear is up and you're stabilised the flight, then select TOGA. Or adjust the rudder trim first once airborne and the gear is up, put the autopilot in, then select TOGA.

5th Apr 2009, 04:57
TOGA won't de-stabilize your situation, if things are going well, though until things are under control, leave it at Flex..

..as for the advisability of taking TOGA - do you really want to potentially miss an obstacle by 35 feet?

When in doubt, use the thrust...

5th Apr 2009, 05:27
Adding TOGA once you are stabilized is not much more difficult than adding power on a single engine approach: you just have to add a bit more rudder. However, your climb performance will increase dramatically, and as someone mentioned, the aircaft is easier to handle with the extra thrust (A320).. So, just af the FCOM says!

Just make sure you are stabilized from the initial wobbles.

Old Smokey
7th Apr 2009, 11:36
I'd like to make a comment, perhaps a significant one, but not being A320 rated need to ask the following question first -

Do your engines have multiple thrust ratings, as well as Flex, or is it just Flex from FULL T/O Thrust only.

I would appreciate an answer. My response, if the engine does have multiple thrust derates (TO-1, TO-2 etc.), relates to possible loss of directional control.


Old Smokey

Lafyar Cokov
7th Apr 2009, 12:07
I was chatting to a test pilot recently who stated that the performance calculations really do depend on ideal conditions and it does take very accurate flying, no detrimantal gusts and an 'average' (gross margins etc) aircraft to achieve the published figures. This all surprised me somewhat and after our conversation I definately came away with the idea that in the event of a V1 failure I would use whatever thrust was available!

The published figures do work but with absolute minimum room for error.

7th Apr 2009, 14:42
In the A320 –during my type rating training which I am undertaking now-I haven’t seen an option for derated Engine only during my current training I’ve been taught Flex or TOGA, I thing the derated Engine Thrust is mainly for A330 and A340 with an optional for A320 CFM engines.

7th Apr 2009, 14:46
From a practical perspective on the FFS which I am doing now I tried both Flex and TOGA with Engine cut after V1 I found it pretty much easier for me when I applied TOGA and as a friend suggested on airbusdriver.net (A320 Technique page) I smoothly rotate in a slower rate than normal until the pitch is a little above 10 and left the side stick, the aircraft went well. But thanks for all contributors for their valuable replies.
Note:I am just in the initial A320 Type rating at Airbus in Toulouse,and don't have any experience on type.

7th Apr 2009, 18:17
As a bit of an aside, I always go:

Rotate (10 degrees)
Make sure the beta target is centred and we're flying where we should be (no emergency turn etc.)

Works for me.

I can't really think of any reason why you wouldn't want to use TOGA? Controllability wise I generally wait until it's flying away safely before giving it the extra.

I believe Monarch SOPs stipulate PNF to give TOGA thrust as soon as an engine has failed?

7th Apr 2009, 19:04
Hoping not to sound silly.

What's the difference between Flex and Derated thrust. I always thought that Flex was just an Airbus term for the same as Derated Thrust for Boeing.

Can someone explain the difference.


7th Apr 2009, 19:18
Airbus procedure always call for setting TOGA after TO and OEI. Please check the nice video from TAP (available everywhere, e.g. on youtube), they are very close to Airbus procedures.

Of course every airline is free to use their own procedure, that's why every operator does it a bit differently.

I never added TOGA thrust but hey, if you think you need it, it's never wrong. Calculations are done without.


7th Apr 2009, 19:41
Proxus - Re: “What's the difference between Flex and Derated thrust”. (www.pprune.org/4295303-post29.html)

Also see the associated thread http://www.pprune.org/tech-log/336684-usind-assumed-temp-thrust-derate-engine-failure-scenario-2.html#post4295303
and the link http://www.pprune.org/forums/flight-testing/190430-b737-b727-afm-limitation-thrust-increase-engine-failure.html

7th Apr 2009, 21:12
proxus - derate vs flex (or ATM) is a very important distinction that any pilot should comprehend. I'm amazed at the number of times this question has come up - This thread deserves a "sticky" category.

One Outsider
7th Apr 2009, 21:38
I'm amazed at the number of times this question has come up

I'm amazed too, and worried. The number of people who think that Flex and derate are different terms for the same thing, is somewhat concerning.

7th Apr 2009, 22:02
Derated and Flex are two different things!

Derated means less than max TO thrust. I don't know Boeing but it seems a synonym for reduced TO thrust. Other manufactor use the term derating for reducing the thrust for a given type, i.e. they reduce the max possible thrust for a certain engine on their airframe. If they do, you cannot go above that or you can override it by "firewall thrust", depending on type.

Flex is a derating method. It's based on assumed temperature. In the end, it's also reduced TO thrust. That's correct.


7th Apr 2009, 23:21
Some thoughts -

The published figures do work but with absolute minimum room for error.

There's not much fat for ASDR, depending on certification basis, but the other requirements are not quite so critical. Certainly there is no room for a casual attitude to getting the takeoff handling correct.

Also there will be no controlabillity issue with TOGA

.. be careful of engine mod status and how fast the thrust ramps up when you decide to go for rated thrust. I was involved in a fatal accident investigation some years ago where the probable straw which broke the camel's back was a Vmca departure associated with a combination of these two considerations. The problem is increased if you are departing at light weight and using a low speed schedule .. especially if you routinely use (and train) for high weight and overspeed schedules.

a high degree of flying accuracy, with any degradation leading to unsatisfactory airspeed / RoC

which is why, for any engine failure with a climb requirement, one needs to have a target ROC in mind to monitor the aircraft's actual performance. If you need a bit more thrust, fine, but be gentle with the throttle(s) and aware of how close you are to Vmca.

What's the difference between Flex and Derated thrust

Flex is using less than rated (maximum) thrust
Derate is using a lower rated thrust (onto which one can add flex)

Conceptually, derate is replacing your V8 with an electronically controlled V6. The concern is that you MUST NOT increase thrust above the lower thrust rating during the takeoff as all the sums etc. are based on the lower value ... and you might get an unpleasant surprise if you firewall the throttles (see OS' post).

I'm amazed at the number of times this question has come up

.. which is why we like to see it resurface over and over again ..

8th Apr 2009, 08:46
Airbus procedure always call for setting TOGA after TO and OEI. Negative, sir. FCTM Single-Aisle:

Consider the use of TOGA thrust, keeping in mind the following:
For a FLEX take-off, selecting the operating engine to TOGA provides additional performance margin but is not a requirement of the reduced thrust take-off certification. The application of TOGA will very quickly supply a large thrust increase but this comes with a significant increase in yawing moment and an increased pitch rate. The selection of TOGA restores thrust margins but it may be at the expense of increased workload in aircraft handling.

Also I always thought that initial pitch is 12,5 deg, where does that 10 deg number come from?

FD (the un-real)

8th Apr 2009, 09:34
I completly agree with you, FD.

If you have been in TLS (or MIA or BEJ) then you know what I mean.


8th Apr 2009, 10:39
Some crew use 10 degrees pitch initially as an aiming point in regards to slightly better acceleration so as not to ever lose speed below V2(an instant failure in the sim).

This initial pitch may occur for a few seconds to crosscheck performance then tweaking back pressure to achieve 12.5degrees pitch.