Artc From Mexico, joined Jan 2011, 14 posts, RR: 0 Posted (2 years 10 months 1 week 6 days 17 hours ago) and read 3507 times:
I saw this video on youtube about a bouncing landing and I noticed that the spoilers did not fully deployed, at least on first touchdown. Is this related to the fact of automatic arming on touchdown? because I dont think the pilots deploy them in sequences... just curious.
gunsontheroof From United States of America, joined Jan 2006, 3480 posts, RR: 10 Reply 1, posted (2 years 10 months 1 week 6 days 15 hours ago) and read 3472 times:
Maybe someone qualified to comment on the ops side of the 732 can shed some more light on this, but if those spoilers aren't all the way deployed, they're pretty close. Looks like a pretty routine deployment of spoilers/reversers upon landing to me.
hal9213 From Germany, joined May 2009, 302 posts, RR: 0 Reply 2, posted (2 years 10 months 1 week 6 days 11 hours ago) and read 3402 times:
I always wondered about this, too, even on all kinds of new aircraft, so would love to hear comments, too.
I always thought, the spoiler deployment criteria would be the same for all spoiler panels (e.g. wheels down and throttles back and whatever else, OR manually deployed) however very often, some of the panels deploy faster than others (as in the video), and some have more deflection than others.
Is that maybe due to hydraulics not being able to instantly supply all spolier panels with pressure at the same time ?
Dogbreath From United Kingdom, joined Mar 2008, 251 posts, RR: 0 Reply 5, posted (2 years 10 months 1 week 6 days 3 hours ago) and read 3220 times:
The 737 has 6 spoiler panels on each wing (12 in total). The outer and inner panels on each wing are ground spoilers and the 4 middle ones are flight spoilers. The panels are numbered from 1 to 12. Starting on the left wing the outer is No1 and counts sequentially across to the outer panel on the right wing as No12.
The ground spoilers are therefore 1, 6, 7, and 12.
The flight spoilers are numbered 2, 3, 4, 5, 8, 9, 10, and 11.
On approach the speed brake lever is positioned to the 'armed' position for landing. For auto-deployment on landing, the airplane must be less than 10ft RA (Radar Altitude) and the Thrust Levers in the idle position.
Upon touchdown and main wheel spin-up on any 2 main wheels the speed brake lever is automatically positioned to UP and all flight spoilers extend.
The ground spoilers will extend when a mechanical squat switch on the right main gear strut is compressed during the landing phase.
Therefore it can be deduced that in the landing on the video, the pilot landed on the left main gear first followed shortly afterwards by the right gear.
It is true that the spoiler panels deflect to different deployment angles.
On the ground when the speed brake lever is manually or automatically fully extended - the ground spoiler panels 1 and 12 extend to 60 degrees deflection, and panels 6 and 7 extend to 52 degrees. Flight spoiler panels 2, 3, 10 and 11 will extend to 33 degrees and panels 4, 5, 8 and 9 will extend to 38 degrees.
In flight if the speed brake lever is positioned to the maximum in-flight detent position, spoiler panels 2, 3, 10 and 11 extend to 20 degrees deflection and panels 4, 5, 8 and 9 will move to 22.5 degrees.
Ground spoilers do not extend in flight.
Of course flight spoilers are also used to aid in roll control and will deflect on the downward wing according to inputs from a spoiler mixer. This shouldn't be confused with operation of the speed brakes
Hope that helps answer the question.
With regard to hydraulic supply.
HYD SYS 'A' powers panels 1, 2, 4, 6, 7, 9, 11, and 12
HYD SYS 'B' powers panels 3, 5, 8, and 10
Cool, thanks a lot for the detailed information. I always thought all spoilers have the same condition for deployment at touchdown.
Does this principle basically apply for all kinds of bigger aircrafts ? (ground + flight spoilers, different activation and different deflection angle?)
Dogbreath From United Kingdom, joined Mar 2008, 251 posts, RR: 0 Reply 7, posted (2 years 10 months 1 week 2 days 7 hours ago) and read 2635 times:
It's been a long time since I flew the 747 and can't really remember. Only know the 737.
It makes sense though to segregate the ground spoilers and flight spoilers (for landing speedbrake action) as that gives you some redundancy if there's a malfunction of one system. Without speedbrake activation on landing it greatly increases the ground roll.