Roll tendency with a failed slat
Thread Starter
Join Date: Apr 2008
Location: nowhere
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
Roll tendency with a failed slat
I always figured that if a slat did not extend on one wing, the aircraft would want to roll toward the failed slat, but I was assured that the aircraft will roll toward the wing with all slats extended.
Anyone care to confirm.
Anyone care to confirm.
Join Date: Jun 2004
Location: Australia
Posts: 1,843
Likes: 0
Received 0 Likes
on
0 Posts
At high speed and low angles of attack, the aircraft will roll rapidly towards the wing with the most slats extended.
About minimum clean speed, assymetric slats will have negligible roll effect.
At approach angles of attack, the aircraft will have a small tendancy to roll towards the wing with the least slats extended.
At high angles of attack, stand by for the roller coaster ride as the wing with the least slats stalls first, associated with rapid roll towards the "least slats" wing.
NOTE 1 - Most slats and least slats terms used here to differentiate between "fail" extended and "fail" not extended.
NOTE 2 - DC9 operators will be familiar with the pronounced back elevator required to compensate for lift loss when slats are extended at high speed.
Regards,
Old Smokey
About minimum clean speed, assymetric slats will have negligible roll effect.
At approach angles of attack, the aircraft will have a small tendancy to roll towards the wing with the least slats extended.
At high angles of attack, stand by for the roller coaster ride as the wing with the least slats stalls first, associated with rapid roll towards the "least slats" wing.
NOTE 1 - Most slats and least slats terms used here to differentiate between "fail" extended and "fail" not extended.
NOTE 2 - DC9 operators will be familiar with the pronounced back elevator required to compensate for lift loss when slats are extended at high speed.
Regards,
Old Smokey
Join Date: Sep 2006
Location: Spain
Age: 35
Posts: 313
Likes: 0
Received 0 Likes
on
0 Posts
This reminds me of an exam question.
"Concerning flap and slat asymmetry, which statement is correct?"
ANSWER: "Flap asymmetry will cause a large rolling moment at all speeds; slat asymmetry will cause a large difference in Cl max"
"Concerning flap and slat asymmetry, which statement is correct?"
ANSWER: "Flap asymmetry will cause a large rolling moment at all speeds; slat asymmetry will cause a large difference in Cl max"
Thread Starter
Join Date: Apr 2008
Location: nowhere
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
The TWA thing is a separate issue. My original question referred to a failure of a slat to extend when the rest do. More specifically I am referring to low speed situations such as during normal selections.
From actual experience:
DC10-30
Decelerating on base leg, approx 210 kts & 5 degrees NU, Flap 0/EXT selected (extends slats). Left outboard slats did not extend. Full right aileron input plus about 2/3 of full right rudder required to keep approx straight & level. After cycle back to UP/Retract and back again, normal conditions returned. Scary moment....
DC10-30
Decelerating on base leg, approx 210 kts & 5 degrees NU, Flap 0/EXT selected (extends slats). Left outboard slats did not extend. Full right aileron input plus about 2/3 of full right rudder required to keep approx straight & level. After cycle back to UP/Retract and back again, normal conditions returned. Scary moment....