Gear Down...

[yafb]

Finally, a real question for the heavy iron flyers :-) ...

I was idly watching a United A320 departing San Jose (KSJC) this afternoon (I work a few hundred metres from SJC VOR) and I noticed it kept its gear down until pretty much out of sight (i.e. probably a couple of miles out). Is this done for some sort of gear-cooling reason or something like that? I've seen it once or twice before in different locations over the years.

-- Hamish

[dashtrash400]

Most likely was a gear-down ferry flight...I've done a few of those myself. Unless somebody just forgot to bring the gear up...amazingly enough, it happens.

[yafb]

Had to wonder about the forgetting thing, but I just can't believe that happens :-). (I've done it, but doing it on an Arrow at 100 KIAS ain't quite the same thing...).

So what's a gear-down ferry flight for?

[flybarneyjets]

Ferry flight? Possibly. Gear accidentally left down? Not likely, but it's happened (to me). With the A320, it was more than likely required due to hot temperatures and a relatively quick turn. I've been in the jumpseat on United out of Denver when they've had to leave it down to watch the brake thermal units (which are displayed in the cockpit) drop below a certain value before they can bring the gear into the wells.

[yafb]

Thanks -- I've also seen it on heavies (A340's or 747's) flying out of Sydney as well, possibly the result of a quick turnaround from Melbourne on the way to Singapore or something, I guess.

So what happens when you forget the gear? Do you get a "gear down" warning above a certain speed? Does the rest of the crew rib you mercilessly for the rest of the flight?

[flybarneyjets]

Well, I'll tell you my little story.

I was captain on the EMB-120 at a very large (increasingly-so) regional carrier back in 2001. One very foggy morning in Fresno, just after rotation, we ran right through the middle of a small "V" of Canada Geese (5 or 6 of them) that were flying no more than 50' feet or so off the deck perpendicular to our climb-path. We saw them just as we left the ground and the "pucker-factor" negated any standard callouts like "positive-rate, landing-gear up."

We didn't hit a single one of them, but it was a close-enough call that we both were a bit rattled about it. I called for "flaps up" after calming down a bit and climbing through 1000' AGL.

While climbing through about 10,000' feet, I noticed that I was having a difficult time accelerating from our normal climb speed and that we were getting a miserable rate of climb. For a brief bit, we both wondered aloud whether or not we actually had hit one of the geese and done some damage to the airframe that might be keeping us from achieving our normal performance.

Then we noticed that those three little green lights were still lit up.

We never exceeded VLE, so we just slowed down to below VLOR and brought the gear up and headed up to SFO, where we had maintenance do a bird-strike inspection just to be sure.

I told that story on my most recent job interview. The evaluator got as big a laugh out of it as I do when I think about it.

[yafb]

Wow -- thanks. Quite a story -- it's easy to see how and why the gear remained down in your case. Not quite the same as obliviously leaving the gear down while mindlessly thinking about having to mow the lawn when you get home, or something :-).

[dashtrash400]

Interesting, I hadn't realized that certain airplanes needed to keep their gear down after takeoff for cooling purposes when departing after short turns. I figured that if the turn was so short that the brakes were still pretty hot, that'd prevent one from departing due to rejected-TO considerations. In the Q400, we have tables to determine how soon we can depart after braking hard on landing. Doesn't make sense that they'd be cool enough to depart but not cool enough to retract gear. Obvious the engineers did more thinking about this than I did ;-).

[flybarneyjets]

Yeah. I thought it was weird too.

[yafb]

It makes sense to me (more-or-less) -- once the wheel's retracted, any excess heat is either radiated to the (close-by) gear well and other surroundings and / or has no way of dissipating (unlike when it's extended). This can't be a good thing, either for the wheel assembly itself or for the surroundings. Well, that's my theory and I'm sticking to it :-).

-- Hamish

[dashtrash400]

Yeah, Hamish, it makes sense to me why extra heat in the gear well would be a bad thing...it just doesn't make sense why overheated brakes wouldn't be an equally bad thing in case of a rejected TO. I'm guessing that hot brakes in the A320 et all don't lose effectiveness as quickly as my plane, and that's why they have tables for time-to-retract rather than time-to-depart.

Incidently, a friend of mine - an FO on the Dash-8-200 - got in trouble for not retracting the gear. It was actually his leg, the CA called "Positive Rate" and he called "Gear Up"...she simply forgot to actually put the gear up. She didn't catch it on the after takeoff checklist, he didn't catch that she didn't catch it, and they were above Vle before they noticed the poor performance. They fessed up and got a remedial sim session as penance.