Speed Brake/Reverse Thrust B737-200

[Zenj]

Hi Folks,

I have noticed it recently and I can not see it in the books.

When the speed brake lever is in down detent position and while landing you decide to apply reverse thrust, the levers refuse to go into reverse unless you deploy speed brake manually and thats when it will accept to go into reverse.

This is a scenario where you have forgotten to ARM the speed brake before landing.

Any explanation for this please ?

[LEM]

Jambo Zenj!
Very strange feature, and absolutely crazy and dangerous!
Are you SURE it's a -200 feature, and not simply a malfunction or mishandling on that particular airplane?

I would be VERY surprised if Boeing had designed such a feature on earlier 737s...

I flew the advanced -200, but I can't recall such a dangerous feature...

On the contrary, first of all you can always pull reverse thrust on a classic, even before touchdown, below 10 ft RA (although prohibited, this is a safety feature in case the air ground sensor is not triggered upon touchdown... and coud save your day if you are floating badly on a short runway...).

Second, the system is designed in a way that even if you forget to arm the speedbrakes, they will extend automatically when you pull reverse thrust, exactly as it happens during an aborted takeoff.
Some operators even adopt in their SOP this sequence during RTO, to save some tenth of a second: close the throttle, pull reverse, THEN make sure the speed brakes have extended.

IF it works, you definitely gain a few tenth of a second, but I disagree on this procedure... search for some interesting thread on this subject on this forum, it has been discussed at lenght before.

Happy flying in my beloved Africa!
LEM

[Centaurus]

As LEM says, if you forget to arm the speed brakes before landing in the 737-200 and Classic, the lever will come up automatically on selection of the reverse thrust lever (s). While some airlines (again, as LEM has noted) use the reverse thrust levers as the first action in an abort to get the speedbrake lever up, this procedure is contrary to the Boeing recommendation. The speedbrake actuation by use of the reverse thrust lever is in fact the back-up action in event of the pilot forgetting to extend the speedbrake lever on an abort.

The ground and flight spoiler extension is absolutely vital to effective wheel braking and selection of speed brake lever up as the first action after throttle closure (assuming RTO is operating), ensures the weight is on the wheels quickly. On the other hand, with a severe damage engine failure where difficulty may be experienced in getting the reverse thrust levers up straight away, valuable seconds could be lost because the speedbrake lever is still down and RTO is not being able to do the job properly.