gear down?...what was up?
 

Hi all,
I was watching the operations at ORD on Saturday, when the tower mentioned to an aircraft(B767), "do you realize your gear is down?" There he was, directly over the field at about 4000ft heading about straight North with his gear all down. I didnt catch the response back. I just watched him continue North before he went out of sight, all the while gear down. He never turned or climbed and showed no sign of coming back. I watched him in the nocs for 20 miles or so. I dont think it was any kind of situation. Any ideas please?

There are many reasons why the gear will be left down after takeoff, one of them is brake cooling.

Mutt

Yonks ago whilst working as AIR DEPS controller at Heathrow I advised an Air France a/c that his gear was down some time after take off and received the reply: "Yes, we use it for the take-off m'sieur".

Bwah ha ha ha....... OW ...... oh, my ribs! <ROTFLMAO>

Love the French pilot's understated humour.

Hmmm, there's a thought. Wonder if he was serious?

:) :) :)

In Borneo [decades ago] Tower asked for confirmation that xxx123 had 3 greens [strip said Twin Pioneer]. After the fifth or sixth call, the captain replied "Roger, three greens, DOWN, LOCKED ANF F**KIN WELDED"
we aim to please, it keeps the cleaners happy

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chiglet

Ahh thank you for the responses. I was stumped. Sounds perfectly logical.
Now MUTT, Could you please tell me of other reasons? You got me wondering what else would justify gear down after T/O, in a normal situation of course.

On most modern airliners, the gear doors are retracted except when cycling. The drag associated with dropping the doors can be significant enough on a hot and heavy takeoff that it's better to leave the gear down while establishing a sustainable rate of climb.
I can't explain why a 767 at 4000ft directly(?) overhead the field would do so though.

Paper Tiger, Yes, the 767 was directly over the field at around 4000' when the controller stated the gear was down. I wish I was able to hear the response. Another strange thing is that all departures were on North headings (32L,R, 4L), so the A/C had either turned South after TO and then circled back North at that level, or was making an approach to MKE from another airport altogether. It was interesting.

NewsWatch,
Milwaukee (Mitchell)
Just a guess that he was headed there.

Short term reasons.

Brake inoperative or removed, gear stays down for 2 minutes to allow the wheels to spin down.
Nose wheel buffer missing, gear stays down for 2 minutes to allow the wheels to spin down.

Longer term reasons.

Brake cooling, especially is you are taking off from a hot airport on a short flight.
MEL item requiring a gear down flight (We are not allowed to do this with pax)

Can anyone think of anymore?

Mutt.

(Needless to say, these may not apply to all aircraft types)

PaperTiger:

Surely leaving gear down causes more drag than doors?

Or do I have this wrong?

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Live long and Prosper.....

swashplate
Leaving the gear down does cause drag of course but for a short time during the retraction cycle, the gear and the doors are down resulting in more drag. Also the movement of the gear and doors relative to the wings disrupts the airflow slightly.

Normally none of this makes any difference so the gear is retracted as soon as +r.o.c. But in a departure close to the limits (was going to say marginal) you might want to avoid any extra drag, however slight.

Not an everyday practice to be sure but I have seen it done more than once, most notably on 747s leaving Miami for Europe on a 90deg afternoon. The climb angle (or lack thereof !) on those guys has to be seen to be believed. More than once I have been afraid they'd run off the end of 09R but thankfully none did.

paper tiger,

i'm sorry, but your idea of leaving the gear down because of the increased drag of the geardoors sounds like a lot of BS to me. I've been flying B 747-400 for quite some time now, but we NEVER use this practice.

Slam dunk.

slam_dunk
I may well be the victim of an urban legend, but this explanation has been given to me by three separate unrelated people. None of whom was a 747 captain it must be said, and it obviously doesn't apply to 737s - no doors !.

First time I saw it (a 767), I just said hmmm and let it go. But it's intrigued me ever since the MIA episode. I had a clear view of the departure path as we loaded. A Springbok took off immediately followed by Iberia (both -200s I think), both left the gear down and both climbed at a very shallow rate. I watched them out of sight and doubt either got much above 3000ft in that time, wheels still dangling. This (extra drag) reasoning made more sense to me than the brake cooling one, but I would certainly welcome a definitive explanation.

[This message has been edited by PaperTiger (edited 28 June 2001).]

Paper Tiger,

There is no procedure in any of the 18 commercial airliner types which we operate which allows the crew to leave the gear down after takeoff for drag reduction.

The dunlops are retracted by the end of the runway, drag therefore isnt a factor. However if for any reason you care to leave them down, the performance decrement associated with the increased drag must be accounted for. This usually takes the form of a weight reduction and would therefore nullify your argument regarding "minimal" takeoffs!

I could however find you procedures and brake cooling charts which relate to leaving the gear down for brake cooling!

Which would you rather believe?

Mutt http://www.stopstart.fsnet.co.uk/mica/PNTSAce.gif

[This message has been edited by mutt (edited 29 June 2001).]

I'll believe you and the books http://www.pprune.org/ubb/NonCGI/redface.gif
So how long is the gear left down to cool the brakes, and why would they need cooling anyway ? All these guys did was taxi to the threshold and hold for a couple of minutes.

PaperTiger--
It would depend on the length of the taxi to the runway. For example, at the old DHA airport, the taxi to 34L could approach 4 miles, and on a hot day, brakes and tires become very warm indeed.
In addition, prior to gear retraction, the landing gear bogie must in a certain position (truck level for example), so as not to be jammed into the wheel-well. If there are indications of this problem, there are procedures with each particular type to cater for this eventuality, and the flight crew needs time for these procedures to be completed. In busy terminal areas, it is often desirable to "fly the aircraft" and at a less busy time, attend to the landing gear problem.

Could have had a wheel well fire warning - requires gear down for 20' to let it cool. (Although they'd probably land back for that). How about a gear down transit flight to the maintenance base - perhaps with damaged gear doors / retract mechanism?

Surely, if putting the gear up causes the aircraft to stop climbing while the gear is being retracted, this is illegal? JAR /FAR regulation stipulate a minimum ROC after T/O for obstacles etc. If you can't make that, you are too heavy to airborne. The only time you are allowed to fly level is to accelerate during flap retract. Interesting rumour though.

OK, I'm persuaded to the brake cooling thing given that two consecutive departures did it. The odds of both having some kind of mechanical must be close to 0 - didn't see either land back, but that would have taken a while anyway being close to MTOW.
The taxi for 09R at MIA is effectively an 11,000 ft backtrack, so presumably the decision for a gear-down climb out would have to have been made before leaving the gate.
But back to bigjets' question - what was that 767 doing at ORD then ?

PaperTiger,

Think back to the Nationair DC8 crash in Jeddah, Saudi Arabia in 1990 (?).

Mutt http://www.pprune.org/ubb/NonCGI/frown.gif

Being that it was an American company 767, would seem unlikely that it would leave Chicago if it had a gear retraction problem. Most confusing is why we was where he was doing what he was doing. I dont mean to make a mountain out of a molehill Im just nosey. I havent slept since the incident and im a little cranky. AA wont return my calls and my wife is leaving me....

Okay, BigJETS I'll put you out of your misery. The guy was leaving it down to let the snow and slush blow off the gear before retracting it so that those little itsy-bitsy switches didn't freeze during the high altitude cruise and cause problems.

(Seriously, there was an ac I flew where we retracted/extended/retracted after take-off in such conditions to avoid just that. But I can't remember which one it was)

Okay... ODR in June... well...

Could be that he had a problem with the hydraulics or in raising the gear. In these situations you stabilise at a sensible altitude and work through the checklists.

Or - he could have been flying gear down to a maintenance facility at another field to let the contract or company engineers fix the jet.

thanks for the replies. I suppose he could have been doing a maintenance run. Interesting that he came from the south while depratures from OHare at the time were northerly. There is a facility at the old Wurtsmith AFB in Oscoda MI (north-eastern lower peninsula) which was the direction he was headed. Im not sure American would use the services there or even what they do exactly there. I would think any such problem would be provided for at OHare.

Could it have been training related?