B737 Landing Gear overspeed

[jonesthepilot]

What IAS would need to be exceeded to cause a landing gear overspeed on retraction on a B737?

[BOAC]

236kts is an overspeed. I cannot quite see how one can exceed this limit, but if it has been done, the engineers will look in the MM and take appropriate action. That may be Nil for a small exceedance, inspect the doors for a bigger one and go look for the doors in the countryside for a huge one.

[citizensun]

yep, 235kts is max for retraction~

[IRRenewal]

I cannot quite see how one can exceed this limit

How to do it?

Accelerate to 250K with the gear level in the 'up' position. PM selects the gear lever to 'down' rather than 'off', exclaims 'oh sh!t' and selects 'up' again.

It's been done many times and I'm sure it will happen again.

[hetfield]

Okay, s..t happens.

If afterwards everything seems to be normal, continue flight BUT put it in the tech log

[jonesthepilot]

overspeed l/g retraction

thanks guys. my next question is then how did Jet2 manage to overspeed on gear retraction on sunday 5 sep out of lba at about 0810z. this required a return to lba for engineering checks as no engineers available at destination. not looking to find out if it was a cock up but more intrigued to find out why it could have happened. Vr to gear retraction limi?t has got to be at least 90kts. what was going on during that time. If it was a757 then the margin is even greater.

[Pitch Up Authority]

Another way to exceed is when you need to loose altitude quickly and reduce speed at the same time. You would use the gear and overlook the retraction speed limit when retracting it.

[BOAC]

Inattention I guess. They either 'forgot' to raise it and/or had not been properly trained in selecting gear 'OFF' as per IRRenewal's post.

[Denti]

Yup, most likely. We changed quite a few years ago our SOP after such an incident and since then gear lever to off has to be done in the same move as flaps up (and outboard landing lights off/retract).

[RAT 5]

Another way to exceed is when you need to loose altitude quickly and reduce speed at the same time. You would use the gear and overlook the retraction speed limit when retracting it.

Now that's an interesting scenario. If you want slow down and lower gear it is likely to be because of an inimment landing. If you want to raise the gear after extending it as a speedbrake/descent rate controller it implies accelerating again. Now why would you do that? Only for a G/A, surely, and then there is no overspeed issue.

[dixi188]

RAT5

Not 737, but our A/C has 270 kts limit for gear down and 240 kts for gear up, so thats how it could happen.

[cosmo kramer]

When the gear goes down, it stays down.

If you need to extend and retract the gear to descend, something went terribly wrong with the descend planning or you are complying with an unreasonable request from ATC, where the better response would have been "unable"

[IRRenewal]

Denti wrote:

Yup, most likely. We changed quite a few years ago our SOP after such an incident and since then gear lever to off has to be done in the same move as flaps up (and outboard landing lights off/retract).

I can see where this is coming from, but it creates the risk of dropping the gear again while still (trying to) accelerate and retract the flaps. In a single engine scenario this could end up fairly messy.

[Denti]

Yes, i guess it could. However we do accelerate at min 1500' and in OEI cases with close in terrain often above MSA which assures terrain clearance. And since speed is not a problem at all you can raise it again straight away.

[BOAC]

The safest way (and the way I was taught) is to

a) wait until clean (not until checklist is called)
b) push inwards on the lever while moving it down so it is pushed into the detent and DO IT SLOWLY AND DELIBERATELY