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RTO in a 737 NG

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RTO in a 737 NG

Old 1st Jul 2010, 16:32
  #21 (permalink)  
 
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One other thing, the speedbrakes will raise when the reverser levers are positioned for idle reverse , which will happen not earlier than engines go down to idle thrust. This takes about 2 seconds , so you won't have automatic raise of the speedbrakes untill about 2-3 sec from deciding to RTO.
By Boeing procedure (for the 737 ) , the Cpt will retard the thrust then raise manually the speedbrakes. The engines will be at idle thrust at which time the lock will open and allow reverse thrust application.
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Old 1st Jul 2010, 16:53
  #22 (permalink)  
 
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Centaurus, agree 100%.

Some of us flew a/c like the B707 where there was no auto speedbrake function so to me it is quite natural to make the manual selection on the RTO (or even a normal landing).

Boeing also use the word "simultaneously" which I believe means "at the same time"!
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Old 1st Jul 2010, 17:33
  #23 (permalink)  
 
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The auto speedbrake function on the 737 is just that...a function. As continually said here, it can malfunction!

In the heat of the moment during any RTO there is always potential for something to go amiss, although in my experience it is usually during the later stages when the aircraft has finally came to a stop and malfunction diagnosis, followed by memory items and a possible resultant evacuation occurs (ie NOT stowing the speedbrake lever or ensuring flaps have reached 40 degrees. This has all been observed (thankfully only) in the simulator.

To me the PM call 'speedbrake' or 'no speedbrake' is worth it's weight in gold here. Immediately after any touchdown and equally as soon as an RTO is initiated.
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Old 1st Jul 2010, 18:20
  #24 (permalink)  
 
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In my company JAR operator and in fact in every sim i have every been in all boeing, all performing boeing sop's you would without question fail your RTO section of the sim if you didn't manually move to, or if your quick extend the speed brakes.

That from my point of view is the legal part for you black and white.
Talk it through and keep it calm:

STOP,
DISCONNECT AND RETARD,
SPEED BRAKE DEPLOY, (At this point the a/c will pitch nose down as the brakes kick in.)
CHECK RTO BRAKING MANUAL IF IT DOESN'T WORK, HEELS ON THE FLOOR IF IT DOES,
REVERS THRUST AS NESS.
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Old 1st Jul 2010, 18:33
  #25 (permalink)  
 
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Remember Guys/Gals the QRH is vetted by lawyers & Boeing, they try to publish a watertight procedure so that everything is covered correctly if they go to court......for this reason, speedbrakes are manually deployed before selecting reverse......same procedure on 777..

Last edited by zlin77; 1st Jul 2010 at 19:04.
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Old 1st Jul 2010, 23:11
  #26 (permalink)  
 
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Our procedures to manually raise the speedbrake before initiating reverse thrust were introduced in 2008.

The reason given was due to a tech insertion on later model engines (improving gas flow). This required a new FAA test program that included new requirements for load testing.

The load analysis tested effect on engine components when during an RTO there is limited time for spool down before reverser sleeves translate. If using the auto speedbrake method, the sleeve movement may exceed the design load case. When using the manual speedbrake method, the design load was not exceeded (only an extra second of spool down is required).

Thus the change to SOP's, to require manually raising speedbrake first.

There is no change to field performance as the manual method is used during certification.
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Old 2nd Jul 2010, 00:44
  #27 (permalink)  
 
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The engines will be at idle thrust at which time the lock will open and allow reverse thrust application.
Not so, I fear. In a rejected take off from high power, the N1 will have dropped to around 50-60 percent N1 on the way down to idle reverse N1 by the time the throttles hit the stops and the reverse levers are raised.

The action of lifting the reverse levers towards the first detent is what brings up the autospeed brake - not the idle N1 setting. That is why for landing, as soon as touch down on the main wheels occurs reverse should be selected rapidly to take advantage of the relatively high N1 occurring as the engines wind down.

If the throttles are closed at the flare and touch down occures (say) three seconds later the N1 at touchdown will be around 45 percent N1 on the way down to 31% N1. If, at four seconds after touch down, reverse has not been selected, the idle N1 will then fall to ground idle of 22 percent N1
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Old 2nd Jul 2010, 02:07
  #28 (permalink)  
 
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In all four airlines I've flown the B737 for the TRE/checker would de-brief the Captain if manual spoilers were not deployed after thrust lever close and auto-throttle disconnect. By itself not a fail/pass item.
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Old 2nd Jul 2010, 17:53
  #29 (permalink)  
 
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Centaurus :
During an RTO positioning the thrust levers to idle thrust and raising the reverser levers to lock will not raise the speedbrakes.
When the sleeves are fully opened ,then you may select reverse thrust, at which time the speedbrakes will deploy.
You may be right, it may not be a question of N1, I am not sure about that.
But it is a delay from the moment you raise the reversers untill you are able to raise the reverser lever to command reverse thrust., about 2 sec, I guess.
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Old 2nd Jul 2010, 22:07
  #30 (permalink)  
 
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How can you confirm the operation of RTO autobrake?
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Old 2nd Jul 2010, 23:33
  #31 (permalink)  
 
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How can you confirm the operation of RTO autobrake?
A glareshield shaped dent in one's forehead is usually a good indication.
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Old 3rd Jul 2010, 14:44
  #32 (permalink)  
 
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It's all in the Certification

The reason for Boeing having you manually deploy the SB is simple:
The accelerate-stop distance published in the AFM, and on which all takeoff calculations are based, is based on Maximum Manual Braking and Speedbrakes deployed. The reversers are a bonus not accounted for during calculations.

Therefore, Boeing wants you to first do the two things that will absolutely guarantee that you stop on the runway: Brake and get the SB out.

In order to safeguard for pilot error, they put in RTO which will brake for you if you forget to, and auto-SB which will get them out for you if you forget them.
The auto-SB is intended as a safeguard and not as a primary means of deploying the SB.

Changing the QRH and the order of critical action items during a rejected takeoff is possible, but the airline has to take responsibility and have it approved by their CAA.

For a system to be considered as reliable enough to serve as primary means of operating something, and basing critical takeoff computations on the assumption that it will operate, it has to be of a certain reliability level.

I do not know if the auto-SB system meets these reliability standards to be considered as a primary system with the checklist only having you verify it's operation.

Do you?
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Old 4th Jul 2010, 16:21
  #33 (permalink)  
 
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I was asking for that...

But seriously - is that the only way? I was thinking that the autobrake disarm light being extinguished would not give you the info as maybe in never armed.
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Old 4th Jul 2010, 16:40
  #34 (permalink)  
 
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Plus; if you have 1 procedure, and the point about T,R's being a bonus anyway is well made, then when 1 or both T.R's are locked out you will not waste valuable time trying to tear the levers from their mounts. KISS
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