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2 All Pilots: Gear Down Enroute  
User currently offlineHush-kit From Germany, joined Sep 2000, 124 posts, RR: 0
Posted (12 years 2 months 1 day 9 hours ago) and read 1620 times:

question 2 all trans-atlantic pilots:
on my last trip from cdg to jfk (DL, 763) I am sure
the main gear went down and after a while
(maybe 2 or 3 minutes) it was rejected
while enroute over canada, about 1, maybe 1 1/4
hour before touchdown at jfk ! Is that common ???
(Never experienced it on all my transatlantic flights)
What could be the reason ???
AND GUYS: It was the gear what went down, no flaps or anything else,
it was that typical gear down noise!!!
Any ideas why that happened are welcome.
CU here
Hush-Kit

12 replies: All unread, jump to last
 
User currently offlineNormalSpeed From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 2 months 1 day 6 hours ago) and read 1506 times:

Are you absolutely sure it was the gear? I mean, sometimes those sounds can be decieving. A gear extension at enroute speeds would probably cause a lot of damage to the landing gear itself, if not rip it off completely.

User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 35
Reply 2, posted (12 years 2 months 1 day 6 hours ago) and read 1478 times:

What do you mean the gear went down and was rejected?




You're only as good as your last departure.
User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 35
Reply 3, posted (12 years 2 months 1 day 5 hours ago) and read 1460 times:

I guess you meant the gear was retracted after a couple of minutes.

One plausible scenario is perhaps he got a faulty gear indication. With the gear up and locked, there should be no lights on.

If he had a gear door unlock indication, or an unsafe gear indication (red light) or even an EICAS fault message, he probably cycled the gear in accordance with his checklist to check/clear the fault.

I'm sure before the gear was extended and retracted the aircraft was slowed to the safe gear extension speed.



You're only as good as your last departure.
User currently offlineJetpilot500 From United States of America, joined Nov 2000, 78 posts, RR: 0
Reply 4, posted (12 years 2 months 1 day 5 hours ago) and read 1443 times:

Even if they did slow down, most airplanes have a maximum altitude where they could cycle the landing gear, usually 20,000' or so. I'm not sure what the limitation is for, maybe structural integrity of the airframe while it is pressurized?

User currently offlineJetpilot500 From United States of America, joined Nov 2000, 78 posts, RR: 0
Reply 5, posted (12 years 2 months 1 day 5 hours ago) and read 1431 times:

Sounds a little fishy to me, I really doubt the landing gear was cycled.

User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 6, posted (12 years 2 months 1 day 3 hours ago) and read 1416 times:

Who knows what he heard, but-

Even if gear extension speeds are exceeded, there is no way dynamic loading would be sufficient to "rip the gear off"...

The loads imposed on a typical landing are far greater than the dynamic loads from a 300 kias airstream. The limit is there due to avoid the aerodynamic disruption created by the gear at higher than limited speeds, which can lead to control issues.

Many a/c have, as part of their CDL, reduced speed limits if some of the fairings on the gear are removed due to the fact that these FAirings could flutter or be damaged at higher airspeeds-but the gear isn't going to be ripped off (come on!)


User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 35
Reply 7, posted (12 years 2 months 1 day 1 hour ago) and read 1374 times:

Can't find my old 767 manuals but,

757 gear extend placard speed.....270K - .82M
757 gear extended "......."...........320K - .82M

DC10/MD10 gear limit speeds
Extend 260 KIAS/.70M
Down..300 KIAS/.70M
Ret.....230 KIAS/.70M

777 gear retract & extend placard speeds
270K/.82M

It would appear from these numbers that the Douglas is more sensitive to altitude when cycling the gear than Boeing.



You're only as good as your last departure.
User currently offlineHush-kit From Germany, joined Sep 2000, 124 posts, RR: 0
Reply 8, posted (12 years 2 months 11 hours ago) and read 1298 times:

Hi FDXmech,
You wrote: "A gear extension at enroute speeds would probably cause a lot of damage to the landing gear itself, if not rip it off completely."
Remember mid-summer 00, when a German 310 (Hapag
LLoyd) opert'd with extracted gear the entire route from a Greek island ( bound for HAJ ), and finaly
made an emergency touch down in Vienna, cause they were running out of fuel ???, see the pic:
Click for large version
Click here for full size photo!

Photo © Marcus Weigand


In my case, I guess they had a false alert on I-don't-
know-what-it-was, and there were no further incidents
while we proceeded to jfk.
As I said... Never experienced anything like that...
BR Chris







User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 9, posted (12 years 2 months 9 hours ago) and read 1287 times:

While the gear probably could take it (although I for one wouldn't try it - who knows what the aerodynamical forces might do to a hydraulic line at M.85) it is likely that gear doors etc wouldn't. Note that for many aircraft, there's a lower speed limit for operating the gear than for having it extended. Part of the reason is that when the gear is fully extended the gear doors will be flush again.

Cheers,
Fred



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 35
Reply 10, posted (12 years 2 months 9 hours ago) and read 1281 times:

Hello Chris

I didn't post the "damage at enroute speed" thread.

I wrote the possible scenario of a gear "up and locked" indication problem directly below it, and some gear placard speeds below that.

Also, I checked the MD10 redtabs and it confirmed that cycling the gear (within the IAS/M envelope [no altitude restriction) is standard procedure for gear unsafe light with gear handle up.




You're only as good as your last departure.
User currently offline727pfe From , joined Dec 1969, posts, RR:
Reply 11, posted (12 years 1 month 4 weeks 1 day 2 hours ago) and read 1181 times:

One possible explanation maybe that the gear is sometimes used as a drag device. Since on most aircraft, the gear can be lowered at a higher airspeed than the flaps, gear is sometimes used. On the aircraft I flew in the past, it was a common procedure when you had to get down fast, but did not want to get a large speed increase. Then when you got to the desired altitude/airspeed, you raised the gear and or lowered the flaps.

User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 12, posted (12 years 1 month 4 weeks 18 hours ago) and read 1142 times:

It would be a poor design indeed, if the hydraulic lines weren't an issue at a max gear extension speed of say 250 kias, but were in danger of failing due to aerodynamic loads at max limit of, say, 320 kias.

That's only 128 % of the normal, operational limit...

I said fairings, as not all a/c have gear doors...


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