gear down?...what was up?
Guest
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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?
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?
Guest
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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
we aim to please, it keeps the cleaners happy
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chiglet
Guest
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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.
I can't explain why a 767 at 4000ft directly(?) overhead the field would do so though.
Guest
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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.
Guest
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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)
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)
Guest
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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.
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.
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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).]
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).]
Guest
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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
[This message has been edited by mutt (edited 29 June 2001).]
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
[This message has been edited by mutt (edited 29 June 2001).]
Guest
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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.
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.
Guest
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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.
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.
Guest
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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 ?
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 ?
