pilotss

Good stuff to think on...I am learning a lot by studying for this interview.

question on the 767. Are the speedbrakes auto activated prior to the manual deployment? Here is my reason for asking. The coefficient of braking is dependent on the amount of fricgtion force applied and friction will depend on weight. If your wing is still producing lift your braking is not as efficient as it should be. I believe most ground spoilers deploy at WOW and antiskid kicks in at a function of speed. Autobrakes are synched to the spoilers in the bus. The spoilers will deploy prior to the autobrakes even at maximum. Autobrake levels are synched at a time duration from the time they are allowed to deploy again depending on spoiler activation. Brakes can't be applied on landing or you'd slam the nose down. Spoilers occur at touchdown. Anyone have different info on spoiler activation? Are yours completely manual? So many aircraft and I am sure there are tons of differing techniques.



For a reject I have to do some research.

I'll check over with the guys at pprune and see what I can dig up.

Thanks for the input. Good discussion.

CE the FTH is the Flight Training Handbook, a basic FAA publication. They have a small chapter in the back that involves jet flying. Also I don't think that you have to wait for the TRs to fully activate until braking occurs. I believe you want the TRs activated first then brake. Some aircraft you must be careful on activation due to the high rear thrust line position. But you can use TR activation before the nosewheel hits the ground. I was thinking the activation sequence.

Lets hear some thoughts.

Cheers,

CE750

good thread indeed, and I agree with you about the importance of braking effectiveness by adding spoilers. I know the MD-11 will automatically deploy them if the throttles are retarded to idle on a takeoff roll (I want to say past 80kts), and I am told the 767 does the same. With that said, the question doesn't address automatic systems, as we also have autobrakes that will kick on when the throttles are retarded to idle on a takeoff roll... I think this is more of a manual aircraft question.. Priority should be on getting the brakes going first then the rest I think.

Would be nice to be able to ask the DAL people what the answer is after one takes the test, buy somehow I don't think they'd tell!

Split S

When I asked the proctor, he said they don't give you your scores or answers just tell you that you passed. If you fail I think they may go over some of the areas that you had difficulty with. At least that's how they ran it on my interview day, no one got their scores they just got the job or got the "Thanks for coming".

CE750

ok, keeping this fun... now what is this crap about climbing out to your alternate at L/Dmax?? That would yield for a most uncomfortable deck angle, no?

StripAlert

Can't vouch for the 767 (yet), but on the 74, the spoilers deploy on an RTO with the reversers (number two, particularly, if I recall correctly). Doesn't surprise me that our manuals mirror the Delta procedures, considering C360's pedigree.

You are correct that the maximum available friction force of the brakes is directly proportional to the normal force between the tires and the runway, and that deploying the spoilers will dump lift and significantly increase that force. However, that does not mean that the brakes are completely ineffective before the spoilers are deployed. Quite to the contrary, on an RTO, applying the wheel brakes expeditiously is the absolute fastest way to begin dissipating energy and get the airplane transitioned from go to stop. Applying "maximum braking" immediately. combined with an operational anti-skid system, will ensure that you get all the available braking effectiveness working in your favor while the reversers deploy, consequentially deploying the spoilers and thereby reducing lift, increasing the normal force between the tires and the runway, and increasing braking effectiveness.

As someone else mentioned, this can be contrasted to the normal landing procedure where saving the brakes and minimizing brake energy are the prime concerns, and going off the end of the runway is unlikely. In that event, spoilers auto-deploy on touchdown, and their initial contribution is more in the form of drag than lift-dumping, as the brakes are saved for later. Then reversers, which are most effective at high airspeeds. Finally brakes are used sparingly at the end, if possible, to finish the maneuver.

A high speed abort in a heavy is dramatically different than the same maneuver in an RJ or A320. 830,000 pounds thundering down 9,000 feet of runway at over 120 knots represents a lot of kinetic energy. (Typical V1 in a max gross configuration for the 747 is around 160 KIAS on dry pavement.) For that reason, an engine failure, fire, or another malfunction that makes the aircraft physically incapable of flight are the only things that you'd execute an abort for above 80-100 KIAS. In the event of an RTO above 80 knots, you can count on extremely hot brakes. Much more than that, and you might be lucky to clear the runway before 16 fuse plugs melt.

My point is that, in a heavy, a high speed RTO is not a taxi back and do it over maneuver. Your main concern is stopping on the runway available, and the brakes are going to be sacrificed, so there's no point in trying to save them. Since they are the only thing that is going to elicit an immediate deceleration (even closing out the throttles lags for spool-down), they come first in the procedure, although in practical application, it all happens more or less simultaneously and is largely a matter of semantics, save for airline interview testing.

However, you certainly wouldn't delay closing out the throttles while you reach for the speedbrake lever, nor would you want to put off applying the brakes while waiting for the spoilers and reversers to deploy. Will they be more effective with the spoilers deployed? Absolutely, but that's no reason not to take advantage of their immediate effectiveness in the interim.

Flare Armed

767 Speedbrakes autodeploy on landing with them in the armed position, weight on wheels, thrust levers closed. On an RTO, they autodeploy when you select reverse thrust.

StripAlert

Not necessarily true. On aircraft with twin-tandem gear (more than two wheels per truck), the moment introduced by the braking action is going to be confined to the truck itself. The pivot joint between the truck and the strut won't pass it on. (The procedure for landing with the nose gear retracted in the E-6 calls for application of both brakes and reversers prior to gently setting the nose on the pavement right before losing elevator effectiveness. Can't say as I've done it in the aircraft, but I have in the sim many times, and there's really no noticeable back-force required on the yoke upon brake application.)

oinkflyer

Could someone point me in the direction of the "other non-WFFF" gouge floating around? Thanks

Gretzky

Why? You don't need anything else...

StripAlert

If you're a mil guy or know anyone who is, just ask around. There's some real good stuff floating around the bubba network... The WFFF gouge is real good also.