A320 Crosswind Take-Offs

[Eurotraveller]

Early in my training I'm sure I remember being told that, on the A320 series, during a crosswind take-off any aileron input held during the rotation will not only result in spoiler deployment but also a faster commanded rotation rate (with associated increased risk of tailstrike).

Having searched the FCOMs I can't find any reference to this, does anyone know if it's true?

Thanks in advance,
Eurotraveller

[Tiennetti]

The exact statement is here 3.04.27 P3

However it does not go deep into technical reason or data for that

I don't really understand how the lateral control can affect the "rotation rate", apart of the normal direct relation between stick inputs and surface movement associated with the ground mode

[Eurotraveller]

Hi Tiennetti,

I've seen the bit in the FCOM I think you're referring to:

For crosswind takeoffs, routine use of into wind aileron is not recommended. In strong crosswind conditions, some lateral control may be used, but care should be taken to avoid using large deflections, resulting in excessive spoiler deployment which increases the tendency to turn into wind, reduces lift and increases drag. Spoiler deflection starts to become significant with more than one third sidestick deflection. As the aircraft lifts off, any lateral control applied will result in a roll rate demand.

It seems to refer only to the roll rate demanded once airborne.

As you say, during the initial rotation the aircraft will still be in ground mode, so I suppose the only way that aileron deflection could result in an increase in rotation rate would be if greater elevator deflection were commanded from the same amount of backstick if there was a simultaneous roll input...I have never read anything in the FCOMs or anywhere else to suggest that this is the case.

I'm starting to seriously doubt whether what I was told was true (or perhaps I just imagined it...)

[Che Guevara]

In the case of crosswind, the flight crew should minimize lateral inputs on ground and during rotation, in order to avoid spoilers extension. If the spoilers are extended on one wing, there is a reduction in lift combined with an increase of drag, and therefore, a reduction in tail clearance and an increased risk of tailstrike.

Airbus
Flight Operations Briefing Notes,
Takeoff and Departure Operations,
Preventing tail-strikes at Takeoff

Don't know if this helps...?

Cheers

[Right Way Up]

Try

Air Accidents Investigation: Airbus 500631 (http://www.aaib.gov.uk/publications/bulletins/december_1998/airbus_500631.cfm)

[Eurotraveller]

Right Way Up,
Thanks for that - the report states: Spoiler deployment during rotation has two undesirable effects: it decreases wing lift and it increases the nose-up pitch rate.

I still can't find any reference in the FCOMs about spoiler deployment increasing pitch rate but I'll keep looking!

Che Guevara,
Thanks, I guess the spoiler deployment plus potential increased pitch rate is not the best combination...

[Tiennetti]

Interesting, i've just learned a new thing :)

[Jonty]

There is a pitch up tendency when the spoilers extend on landing, could you be referring to this? Never heard about it during rotation though.

[mcdhu]

Have a read of the FCTM NO 050 - 'Take off' which makes several references to how you should handle a crosswind take off - particularly the Para entitled "Avoidance of Tailstrike"

[320 driver]

Since the A320 spoilers are behind CG they always produce a pitch up on deployment regardless of when.

You will see this pitch up on landing, when you pull speed brake and, as above if you pop the spoilers with a lateral input on take-off.

Having said that, I use a small lateral input in crosswinds and have never had a serious problem. If you keep the input to half a white cross width the spoilers don't usually deploy.

[FCeng84]

For most commercial jet configurations inboard spoilers have both a direct impact on wing lift and an indirect impact of tail lift as the flow over the horizontal stabilizer is disturbed. As a result, inboard spoiler deployment tends to generate a net nose up down pitching moment. In contrast, outboard spoiler deployment tends to generate nose up pitching moment. Care is usually taken during design of spoiler deployment for speedbraking (particularly in-air) to balance usage of inboard and outboard spoilers so as to bound the net pitching moment that results.

The A320 guidance to avoid large lateral stick displacements due to the nose up pitching moment that they generate suggests that outboard spoilers are used more for roll control than the inboard spoilers.

Another issue that this points to is the transition from ground to air and the associated roll control law mode change. For heavy crosswind takeoffs does the A320 pilot have to quickly remove lateral stick input necessary on the ground in order to avoid commanding too much roll rate during climbout? How about the similar transition from air to ground with heavy crosswind when the lateral control mode is switching from roll rate to the ground mode?

[TyroPicard]

320Driver
You will see this pitch up on landing, when you pull speed brake
Pardon? Are you really a 320 pilot?

[waren9]

Tyro

He used a comma instead of the word "and".

I had to read it twice too.

:ok:

[Microburst2002]

The Cessna Citation III has a funcion of the outboard spoilers that enables using them for longitudinal control if the tailplane is jammed.

If I recall correctly, when activating this function only the outer ones are deployed with the spoiler lever, creating pitch up moments by reducing lift behind the CG.

If in the bus when all the spoilers deploy after touchdown you can feel a pitch up, this pitch up would be more pronounced if only the roll spoilers of both deployed.