737 RTO procedure and auto speed brake deployment question

[McLuvin]

SWA RTO procedure has always been Idle, Brakes, Boards, Reversers, as long as I've been there (11yrs). I flew NGs for the USN for 10 years and we just deployed reversers and verified brakes went to RTO and speed brake auto deployment. Do any of you 737 guys have company procedure which requires you to manually deploy speed brakes prior to reverse thrust on an RTO? Is this just a Southwest thing, or Boeing standard? It seems like reaching for and deploying speed brakes prior to deploying reversers instead of doing both simultaneously by applying reverse thrust and letting them auto deploy delays the application of reverse thrust by several seconds, which could mean the difference between stopping at the end of a slick runway, or ending up with your plane sitting on top of someone's car outside the Midway fence. Thoughts?

[ice2x01]

Yes our company policy at Egyptair is manual speed brakes then reversers. I was told its boeing standard.

[FlyingStone]

It's Boeing procedure to ensure you don't exceed the design load limit on the thrust reversers on the B737NG. Nevertheless, procedure applies to earlier models (1-500) as well.

[Skyjob]

Speedbrakes are most effective dumping the lift and to ensure most "weight" is on wheels when braking making this more effective. During an RTO manual deployment is usually not required as automatic deployment takes places, but sometimes it does not. Thus you should ensure deployment prior to selecting reverse thrust, I think this is what SWA is referring to...

So to ensure maximum braking capability is available by ensuring most downward force (cancelling lift effect).

Our outfit, not SWA, certainly advises "Thrust, Speedbrake, Reverse, then monitor RTO or apply maximum manual braking if required".

t's Boeing procedure to ensure you don't exceed the design load limit on the thrust reversers on the B737NG. Not heard of this before...

[CHfour]

@skyjob

Here it is:
BOEING COMMERCIAL AIRPLANES
FLIGHT OPERATIONS TECHNICAL BULLETIN
NUMBER: 737-12-1
DATE: January 31, 2012
This bulletin provides information which may prove useful in airline operations or airline training. The information
provided in this bulletin is not critical to flight safety. The information may not apply to all customers; specific
effectivity can be determined by contacting The Boeing Company. This information will remain in effect
depending on production changes, customer-originated modifications, and Service Bulletin incorporation.
Information in this bulletin is supplied by The Boeing Company and may not be approved or endorsed by the FAA
at the time of writing. Appropriate formal documentation will be revised, as necessary, to reflect the information
contained in this bulletin. For further information, contact Boeing Commercial Airplanes, Chief Pilot – Flight
Technical and Safety, P. O. Box 3707, Mail Code 20-95, Seattle, Washington 98124-2207; Phone +1 (206) 544-
8024; or Facsimile +1 (206) 662-4747.
SUBJECT: Rejected Takeoff (RTO) Maneuver
ATA NO: 0200-00
APPLIES TO: All 737 Airplanes
REASON: To provide background information about the 737 RTO maneuver and to
emphasize the requirement to follow the three-step maneuver.
BACKGROUND INFORMATION
In the 737NG Airplane Flight Manual (AFM), the Rejected Takeoff (RTO) non-normal
maneuver requires the Captain to:
 Simultaneously close the thrust levers (disengage the autothrottles, if required) and apply
maximum manual wheel brakes or verify operation of RTO autobrakes.
 If RTO autobrakes is selected, monitor system performance and apply manual wheel
brakes if the AUTO BRAKE DISARM light illuminates or deceleration is not adequate.
 Raise SPEED BRAKE lever.
 Apply maximum reverse thrust consistent with conditions.
 Continue maximum braking until certain the airplane will stop on the runway.
This is commonly known as a three-step maneuver, i.e., thrust levers, speed brakes and reverse
thrust.
Page 2 of 2
During certification tests for a CFM56-7 engine EEC software upgrade, a remote condition was
identified in which rapid thrust reverser deployment after operating at high forward thrust could
exceed thrust reverser design load limits. This condition was determined not to be unique to this
EEC software upgrade, as the same condition existed in all previous EEC software versions. The
condition is, therefore, possible on all 737NG airplanes.
The 737NG reverser blocker door design is such that the design load of the thrust reverser inner
wall is highest when the translating sleeve is 60% deployed. To prevent exceeding the design
load, the engine must be spooled down before reverse thrust is selected. Tests determined that a
minimum of 3.1 seconds between high forward thrust and thrust reverser deployment was
needed to ensure the thrust reverser design load limits are not exceeded. Flight tests have shown
that this 3.1 second delay can be achieved by sequentially retarding the thrust levers to idle,
manually raising the SPEED BRAKE lever, and then deploying the thrust reversers. Flight tests
have also shown that a two-step maneuver, i.e., retarding the thrust levers to idle and deploying
the thrust reversers, thus automatically raising the speed brakes, does not provide the needed
time delay.
After discussions with the FAA, it was decided that all 737NG airplanes must use the three step
RTO maneuver as described above and in AFM Section 2, Page 14.
For procedural commonality between the 737NG, 737-300/400/500 and 737-100/200, Boeing
will not approve a different procedure for the earlier 737 models.
OPERATING INFORMATION
For the 737NG, the two-step RTO maneuver, i.e., retarding the thrust levers to idle and
deploying the thrust reversers, thus automatically raising the speed brakes, is a violation of
engine certification requirements. These requirements are reflected in the RTO maneuver in the
737NG AFM.
To ensure compliance with engine certification requirements, the RTO maneuver should be
accomplished as a three-step maneuver: close the thrust levers, manually raise the SPEED
BRAKE lever, and apply reverse thrust up to the maximum amount consistent with conditions.
For procedural commonality, the same three-step RTO maneuver is applicable to 737-100/200
and 737-300/400/500 airplanes.

[RAT 5]

1. Speed brakes ASAP maximises wheel braking effect.
2. Auto deployment via TR's might not work. You won't know until you try.
3. Effect of TR's is not included in the stop calculation: normal dry conditions.

Biggest threat to braking on RTO is PF disengaging RTO mode and reducing brake effect.

[Centaurus]

Interesting. I may be wrong, but from what I recall years ago I thought the reason for manual speed brake selection (and not auto speed brake by lifting the reversers) before selecting reverse, was that certification for rejected take off required a one second delay between each retarding action by the pilot. Thus(I thought) the first action of a reject during certification testing was:

Brakes on.
1 second gap.
Next was speed brake (spoilers) manual actuate.
1 second gap.
Next was thrust levers closed.
1 second gap.
Next was thrust reversers actuate.

[Judd]

Biggest threat to braking on RTO is PF disengaging RTO mode and reducing brake effect.
Agree. Which is why it is good airmanship for the PM to closely monitor the auto-brakes operation during a reject and if he sees the autobrake disengage light come on to call "autobrakes disengaged"

In real life however, during a high speed rejected take off, the PM is probably transfixed, eyeballs on stalks, staring ahead at the remaining runway length and not paying attention to the possible appearance of the disengage light of the autobrake system caused by inadvertent pressure on the brake pedals by the PM.

Similarly during autobrakes use when landing. The PM should call "autobrakes disengaged"if he sees the light come on. That is because he probably wouldn't know if the disengagement was due to a deliberate action or inadvertent action by the PF.

On the other hand, the PF should call "manual braking" when he deliberately disengages the autobrakes during the landing run. This warns the PM that the autobrake disengaged light is about to come on.

[RAT 5]

Ah, Judd, the ideal world. You're correct; either eyes on stalks frozen, or transfixed on the ASI because the SOP is to call the speeds. The SOP also says to monitor speed brake & reversers forcing your eyes to the centre and thus towards the Disarm light. If the eyes stay blinkered ahead then all else fails. It's even worse if F/O is PF and captain rejects for an unknown reason. PF had eyes fixed down the runway and there they stay. It takes self-discipline & training = newspaper around the ears, to swap from PF to PM during an RTO.

[Derfred]

Rat5, you are incorrect.

CH answerd the OP's question with a direct quote from Boeing.

It is not about stopping performance, or speed brake ahead of reverse thrust.

The engine manufacturer stuffed up. The fix was that it was cheaper to change RTO procedures than to re-design and re-certify the engine.

Boeing didn't stuff this up, they are just keeping their aircraft flying after an otherwise unrecoverable CFM stuffup.

Dollars :ouch:

[RAT 5]

Your quote about the NG engines might be relevant. It was, in my older humbler days, the procedure from B732 - B733/7/8 to operate manual speed brakes before TR's, and I was always educated that it was for the reasons mentioned. Someone in Boeing, as we have seen in many other systems, decided to take decision making out of the hands of the pilots because they are such dummies and forget things. Oh dear, another good idea in the bin because of an unforeseen consequence. Let's go back to basics.
Now you operate a mixed fleet of classic & NG a/c. The former has the basic method and the later the dummy's method. Is that wise? Are you asking pilots to remember the type and a different SOP on a common type rating? What would you expect the HOT to say? OK, there are airlines with single models, but hey, I thought Boeing procedures were supposed to be common.
I'll ignore your profanity. Not worthy of a professional discussion.

[Derfred]

I apologise for the profanity, that has been edited out.

Boeing was forced to introduce this procedure (manual speedbrake before thrust reverse) with the introduction of the 737NG.

The only reason for this was that during certification, it was identified that the CFM56-7B engine had a weakness in it's thrust reverser blocker doors.

That is the ONLY reason for this procedure. It has nothing to do with stopping performance.

PS: Boeing has amended the RTO SOPs for all 737s, for the reasons you have identified for mixed fleets.

[Judd]

Boeing was forced to introduce this procedure (manual speedbrake before thrust reverse) with the introduction of the 737NG.

Unless I have missed something while reading this thread, Boeing always recommended manual speed brake before selection of reverse from the time the first 737-100 was introduced. It didn't start with the 737NG.

[Derfred]

Ok, I'll rephrase. With the introduction of the 737NG it became a requirement rather than a recommendation.