A 330 THRUST REVERSER AND PITCH UP???
Thread Starter
Join Date: Feb 2001
Location: Milkway Galaxy
Posts: 240
Likes: 0
Received 0 Likes
on
0 Posts
A 330 THRUST REVERSER AND PITCH UP???
Extract from A 330 FCOM PRO-NOR-SOP-19 P 5/6
"A small pitch up may occur during thrust reversers deployment before nose landing gear touchdown"
My experience is just opposite, after extension of spoilers, when Thrust Reverser is deployed before Nose Landing Gear, nose drops faster.
Any idea?
Thanks
"A small pitch up may occur during thrust reversers deployment before nose landing gear touchdown"
My experience is just opposite, after extension of spoilers, when Thrust Reverser is deployed before Nose Landing Gear, nose drops faster.
Any idea?
Thanks
Join Date: Jun 2014
Location: Mordor
Posts: 335
Likes: 0
Received 0 Likes
on
0 Posts
I can only confirm. Reverser selection causes an immediate nose drop and significant back stick input is required.
Having said that, I *think* the cause for the nose drop are the spoilers, which deploy upon rev selection. Maybe later the reverse thrust itself causes some pitch up, but I haven't noticed...
Having said that, I *think* the cause for the nose drop are the spoilers, which deploy upon rev selection. Maybe later the reverse thrust itself causes some pitch up, but I haven't noticed...
Hi S_n_R,
FWIW I think the deployment of the Ground Spoilers (normally at main-wheel spin-up) is likely to produce a noticeable pitch-up, as it does on other Airbus types I've flown.
FWIW I think the deployment of the Ground Spoilers (normally at main-wheel spin-up) is likely to produce a noticeable pitch-up, as it does on other Airbus types I've flown.
No specific knowledge of the A330, but I was directly involved in wind tunnel testing during the investigation of the Lauda 767 crash (after a reverser deployed in-flight).
During that testing, with the reverser deployed, the airflow and lift was destroyed over a large portion of the wing. On a swept wing, I'd expect that sort of airflow disruption with T/R deployment to result in a significant pitch down - not pitch up - moment.
I suspect ahramin and Chris Scott are correct that it has to do with the associated spoiler deployment, not the T/R.
During that testing, with the reverser deployed, the airflow and lift was destroyed over a large portion of the wing. On a swept wing, I'd expect that sort of airflow disruption with T/R deployment to result in a significant pitch down - not pitch up - moment.
I suspect ahramin and Chris Scott are correct that it has to do with the associated spoiler deployment, not the T/R.
Hi ahramin,
Like tdracer, I haven't flown the A330, unfortunately. So can you explain under what circumstances the Ground Spoilers, which are normally activated on touchdown by main-wheel spin-up, would only half-deploy?
Hi tdracer,
Perhaps we have to distinguish between the in-flight situation, when the a/c tends to rotate around its C of G, and the on-the-ground situation where its weight is mostly being supported by its main-wheels on the ground?
In the latter case (on the ground), it will rotate around the main-wheel axles as a pivot point.** Despite the chaotic airflow created by the fan-reverser deployment, the rearward thrust vector it produces is presumably directed above the pivot point. That should produce a slight pitch-up, but I cannot pretend to have noticed it on the A310 or A320.
Early main-wheel braking certainly generates a pitch-down which has to be countered with elevator to avoid a hard touchdown of the nose-wheels. On the A320, for example, medium autobrake tends to start before nose-wheel touchdown.
**[EDIT] In this case, probably the attachment point between the main-gear leg and the main-wheel truck (bogie)?
Like tdracer, I haven't flown the A330, unfortunately. So can you explain under what circumstances the Ground Spoilers, which are normally activated on touchdown by main-wheel spin-up, would only half-deploy?
Hi tdracer,
Perhaps we have to distinguish between the in-flight situation, when the a/c tends to rotate around its C of G, and the on-the-ground situation where its weight is mostly being supported by its main-wheels on the ground?
In the latter case (on the ground), it will rotate around the main-wheel axles as a pivot point.** Despite the chaotic airflow created by the fan-reverser deployment, the rearward thrust vector it produces is presumably directed above the pivot point. That should produce a slight pitch-up, but I cannot pretend to have noticed it on the A310 or A320.
Early main-wheel braking certainly generates a pitch-down which has to be countered with elevator to avoid a hard touchdown of the nose-wheels. On the A320, for example, medium autobrake tends to start before nose-wheel touchdown.
**[EDIT] In this case, probably the attachment point between the main-gear leg and the main-wheel truck (bogie)?
Last edited by Chris Scott; 4th Dec 2016 at 11:00.
Join Date: Jun 2014
Location: Mordor
Posts: 335
Likes: 0
Received 0 Likes
on
0 Posts
Hi,
Partial extension happens only in case of assymetric touchdown and reverse selection - similar to the A320, at least current Mod.
The GND signal for full spoiler deployment comes either from wheel spin up, or (both MLG compression AND RA<6ft).
The latter takes time since MLG is double bogey and normally there's a significant delay between aft wheels touchdown, the front wheels touchdown and the oleo compression (hence usually two distinctive thumps on landing).
My theory was that reverser selection deployed spoilers before AIR/GND logic signal was processed, but I am not so sure anymore...
In any case, after reverse selection on touchdown of the aft MLG wheels two distinctive things happen:
- immediate touchdown (or rather thump!) of the front MLG wheels and oleo compression
- significant pitch-down moment which has to be counteracted by sidestick
If reverse is not selected, the pitching moment is close to neutral, similar to the A320. Perhaps the reason is loss of lift due to airflow disruption as Tdracer described... Never ever noticed any pitch-up though...
Where is A33Zab, when we need him
Partial extension happens only in case of assymetric touchdown and reverse selection - similar to the A320, at least current Mod.
The GND signal for full spoiler deployment comes either from wheel spin up, or (both MLG compression AND RA<6ft).
The latter takes time since MLG is double bogey and normally there's a significant delay between aft wheels touchdown, the front wheels touchdown and the oleo compression (hence usually two distinctive thumps on landing).
My theory was that reverser selection deployed spoilers before AIR/GND logic signal was processed, but I am not so sure anymore...
In any case, after reverse selection on touchdown of the aft MLG wheels two distinctive things happen:
- immediate touchdown (or rather thump!) of the front MLG wheels and oleo compression
- significant pitch-down moment which has to be counteracted by sidestick
If reverse is not selected, the pitching moment is close to neutral, similar to the A320. Perhaps the reason is loss of lift due to airflow disruption as Tdracer described... Never ever noticed any pitch-up though...
Where is A33Zab, when we need him
Join Date: Jul 2006
Location: Somewhere over the rainbow
Posts: 946
Likes: 0
Received 0 Likes
on
0 Posts
Hello guys, I have the same doubt for the A320 and still did not find a definitive answer.. Why the deployment of the reversers would create a small pitch up?
Thanks
Thanks
Perhaps we have to distinguish between the in-flight situation, when the a/c tends to rotate around its C of G, and the on-the-ground situation where its weight is mostly being supported by its main-wheels on the ground?
In the latter case (on the ground), it will rotate around the main-wheel axles as a pivot point.** Despite the chaotic airflow created by the fan-reverser deployment, the rearward thrust vector it produces is presumably directed above the pivot point. That should produce a slight pitch-up, but I cannot pretend to have noticed it on the A310 or A320.
If the gear were not on the runway, a rearward thrust vector below the CG would tend to produce a nose-down pitch. Gear rolling on the runway would do nothing to offset that; they'd just roll a little slower as the nose pitched down.
But I can't seem to sort through this entirely in my head -- obviously a downward force forward of the gear but aft of the CG would create a nose-down pitch.
Join Date: Jul 2006
Location: Somewhere over the rainbow
Posts: 946
Likes: 0
Received 0 Likes
on
0 Posts
I always found that I needed to modulate the joystick in pitch to prevent the A330 nosewheel slamming down after reversers deployed.
Join Date: Aug 2018
Location: Kolkata, India
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Extract from A 330 FCOM PRO-NOR-SOP-19 P 5/6
"A small pitch up may occur during thrust reversers deployment before nose landing gear touchdown"
My experience is just opposite, after extension of spoilers, when Thrust Reverser is deployed before Nose Landing Gear, nose drops faster.
Any idea?
Thanks
"A small pitch up may occur during thrust reversers deployment before nose landing gear touchdown"
My experience is just opposite, after extension of spoilers, when Thrust Reverser is deployed before Nose Landing Gear, nose drops faster.
Any idea?
Thanks