speed brake - airbus
 

Hi guys,

what do you think in the VMO exceeding airbus procedure? especially for speed brake use?

Hi guys,

No one has ideas?

Hi michelda,

the aim is to keep the AP engaged to avoid over controlling with all its associated issues (level busts in RVSM, speed falling below V alpha max, etc..). If the situation is recognised early enough the speed should stay below the protection limit and therefore you can benefit from the AP.

Hi I 2021

You are absolutely right.
But there are two procedure....
One for prevent overspeed and one for recovery.
What do you think about the use of speed brake in the recovery one?

Thanks

What does Airbus say to do?

Airbus says to extend them in case of overspeed.

Airbus says to select speed if speed variations occur around vmo / mmo.

Seems reasonable to me. They built it and flight tested it, presumably to speeds in excess of 0.82.

Airbus says to use them but, in the limitation chapter, they are limited inside the envelope.
So do we use them outside the flight envelope?

For sure airbus tested them at speed above the maximum one but in this case we can flight faster than vmo or higher than max ceiling....

since VMO/MMO exceedance is a precondition for an overspeed recovery, i suppose you're perfectly fine to use the speed brakes as part of the airbus standard procedure to recover from an overspeed condition. also VMO/MMO exceedance is not part of the speed brake inhibition logic. i assume airbus would have integrated this condition in the inhibition logic if it wasn't safe to use them during VMO/MMO exceedance.
i didn't find any limitation on the use of speed brakes in the limitation section of the FCOM (or maybe i'm just too tired already :zzz:).

as you said, i think it is logic to use speed brake during speed exceedance.
But with the wing at high speed and probably with some G force due to high speed protection, is it a good idea to extend spoiler for the wing structure?

In the limit part of the fcom it is reported that there is no limitation in speed for spoilers......for sure inside flight envelope. Outside envelope is a duty of test pilot to understand what is going on and not for a stupid pilot as me.

And given they have given you instructions for what to do when you find yourself outside the envelope, it's a pretty safe bet that a test pilot has been there, tried and tested the procedure -and had it approved.

If Airbus tested and published in the procedures (as it looks like in my manuals in both happenings approaching and exceeding VMO / MMO) this should not lead to personal aurguable judgment (even if based on some knowledge) that would bring only discussion in the cockpit in such a high workload and dynamic situation.

Otherwise we should start now to bring into the discussion the MACH divergence drag number and drop in Cl over Mcrit speed and we would not get out of it anymore.

I like to try to understand always the theory and principles behind any procedures, but as long as they fit and i´m in a healthy plane (not like the one of AF447) i would not willfully disregard any procedures that Airbus tested and reported.

The flight envelope which is approved for use will have been generated by the test pilots exceeding it. For example, Mmo is M0.82. This means the test pilots will have exceeded it, probably by a considerable margin, and by applying appropriate factors to their test flights, the manufacturers have used M0.82 for operations.

What it does not mean is that the wings will come off at M0.83.

Moreover load requirements during the certification phase prescribe a load of 2,5g up to VD, for the A320 family being M0,89 or VD 381kts..so we have a 31kts margin where i COULD pull up the load factor up to 2,5g without creating any structural faiuler or damage. (Offcourse i would not suggest it anyway !)

Bio. To sate my interest in such things, where'd you get that info?

- quite, so would all you 'FBW with computer interference' types PLEASE desist from zoom climbing through everyone else's level when you get a bit fast. IT IS DANGEROUS AND AGAINST THE RULES OF RVSM - AND NORMAL FLYING.

The clue, surely, is in the name SPEED brakes? There are also some levers that control the engines I believe.

If the jet cannot handle the 'excursion' without zoom climbing, then Mmo needs to be reduced for airline ops. Using altitude to wash off energy is for fighter pilots, not airline pilots - and they try to make sure the area is clear before they do so.

Reference in accordance to my company manuals is:

OM-B => FCOM bulletins => 816/1 => VMO/MMO determination

:ok:

Thanks. I can't find it in Flysmart OLB or on Airbus world....

I've found other reference to the same document title on google, so it's not your company title.

I'll keep looking.

Unfortunately i´m not able to make a screenshot of the page as it´s in the closed partition of the company laptop. :{

Found one! Courtesy of a copy of a Central American airline.

I cut and pasted your quoted paragraph into google.

Cheers, I can now sleep with the satisfaction of having learnt something today. :-)

Further to my post #15, I quote this (out of context, but extremely correct!) from the much berated Dozy on the 447 thread (post #739). - delightfully simple, but maybe some prefer to leave it to the software engineers to sort out.:ugh: