Flap alt limitation - a320

[Captain_BH]

hi guys..

Fcom 3 , limitation section, MAX ALT FOR FLAPS 20,000 feet

Is that AGL or MSL ,

what i mean if i operate in airfield that has 5000 ft elevation is the flap max changed to 25000 ft or remains 20000 regardless field elevation!! any idea ? thanks

[DutchOne]

20000 feet is above MSL, as it is an aerodynamic limitation and has nothing to do with the elevation of the runway.

[zlin77]

On 1013 HP......................

[DutchOne]

ISA.........

[Green Guard]

20000 agl ?

...so if Chinese eventually build an airport
below the top of Sagarmata at 21000 ft,
would yo like to fly with your flaps extended at FL410 ?

[Captain_BH]

maybe yes with your aircraft but not airbus

[john_tullamarine]

There are some certification boxes which are more easily (read cheaper - as no-one is likely to want the envelope extended) addressed by ignoring the above F200 situation.

Nothing to stop the OEM removing the restriction .. providing someone ponies up the ante for the certification work.

[John Citizen]

...so if Chinese eventually build an airport
below the top of Sagarmata at 21000 ft,

You would not be able to operate an Airbus here, as the max runway altitude for airport operations is 9200 feet (in the A320 anyway - In the one I fly) (as has already been said)

[John Citizen]

"altitude" is by reference to MSL
"height" is by reference to the ground below you

[john_tullamarine]

.. and anything in the Standards - not otherwise qualified - is Hp.

[MD83FO]

Must must be the Mach Vfe. crossover at FL200 is .5/230
just as the Vle is M .67/280 happens at FL 250

[latetonite]

Equivalent true airspeed is something new to me. But I am sure the flaps do not care about height.

[john_tullamarine]

Flaps, Gear and other speed limited items are designed using Equivalent TAS

I'm not familiar with this term. Do you have any authoritative source for your assertion ?

[Microburst2002]

He means EAS, I'm sure.

I think the FCOM says 20.000 but it means pressure altitude, or FL if you like.
It is an aerodynamic limitation. However I don't know why a thinner atmosphere affects flaps operation.

[ZeBedie]

If airbus wanted to permit flap operation at higher levels, they'd have to have flight tested it but probably decided that it would be a pointless waste of resource to do that.

[blind pew]

The limitation is due to the local airflow going supersonic.
A Trident One lost around 5000ft involuntarily in the Clacton hold when the second officer selected droop upon entering the holding pattern.
The skipper was having a p**s at the time.
It wasn't recorded in the horror comic as to whether he had time to put the old chap away before diving into the cockpit.

[compressor stall]

the max runway altitude for airport operations is 9200 feet (in the A320 anyway)

No it isn't. There are mods and data for ops to a lot higher than that. You just need to pay for it. $$

[Old Smokey]

Equivalent TAS

A bit off topic, but within the spirit of responding to points raised within the thread.............

Equivalent True Airspeed (ETAS) = TAS X Cosine of Drift Angle

It's a Navigational function, not an aerodynamic one, I think that the poster must have meant something else

The 20000 ft Pressure Height limit is so that the manufacturer need not certify the Mach Number limit for Flap operation, as others have indicated. (And as addressed in numerous other threads).

Regards,

Old Smokey

[john_tullamarine]

Equivalent True Airspeed (ETAS) = TAS X Cosine of Drift Angle

Ah, the Jeppesen triangle as opposed to the conventional Dalton. I think I can be forgiven for not realising that in the earlier context.