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ikolkyo
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Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 2:59 am

Anyone able to explain this practice as the tweet asks?

I’d say brake cooling but the MLGs are up, hydraulic related?

Image
Image

https://twitter.com/airlinegeeks/status ... 22720?s=21
 
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airportugal310
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 3:25 am

I think its just the last part of the retraction carefully photographed...the forward NLG door is open, indicating to me that its about to come up any second
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aeropix
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 4:13 am

I’m curious too. This is either photoshop or some kind of problem. The normal retraction sequence has all gear retracting simultaneously and the nose gear doors tend to close before the main gear doors. So it’s not just a “lucky” photo
 
kh1
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 6:29 am

airportugal310 wrote:
I think its just the last part of the retraction carefully photographed...the forward NLG door is open, indicating to me that its about to come up any second


http://www.airliners.net/photo/Korean-A ... ER/1306789

See this for reference. Definitely something going on here, curious as to what.
 
AA737-823
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 8:11 am

ikolkyo wrote:
I’d say brake cooling


Brake cooling of the nose gear, which has no brakes?
I think we can rule that out.
I actually don't think it's necessarily an "issue;" sometimes, actuators get sluggish with age, so it's possible that until the main gear was up and locked, the nose gear or nose gear uplock just took it's sweet time letting go.
 
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ikolkyo
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 8:16 am

AA737-823 wrote:
ikolkyo wrote:
I’d say brake cooling


Brake cooling of the nose gear, which has no brakes?
I think we can rule that out.
I actually don't think it's necessarily an "issue;" sometimes, actuators get sluggish with age, so it's possible that until the main gear was up and locked, the nose gear or nose gear uplock just took it's sweet time letting go.

I said the MLG is up and ruled it out as that being the case. Can’t just quote half a sentence.
 
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SaveFerris
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 6:17 pm

I wonder about the timeframe of both of the pictures. If they were taken on separate days I would say it’s a mechanical issue on both airplanes that coincidentally happened climbing out of Dulles. For all we know the pictures could have been taken years apart. That all having been said the odds of the same issue on two 777s at the same airport on the same day is slim to none.
 
kalvado
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 6:35 pm

Are we sure this is gear retraction, not lowering on arrival? Are those processes just mirrored, or there is a difference?
 
MakeMinesLAX
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 9:18 pm

kalvado wrote:
Are we sure this is gear retraction, not lowering on arrival?

I think the flap position might rule that out. The AoA in these pictures *could* be exaggerated to suggest take-off, though.
 
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kanban
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Re: Interesting photos of 77Es departing with only MLG retracted.

Wed Jul 11, 2018 9:43 pm

dang photographers forgot their nose gear filter
 
cloudboy
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Re: Interesting photos of 77Es departing with only MLG retracted.

Thu Jul 12, 2018 12:35 pm

I didn't realize you could retract just one set of gear - I thought they all worked in unison.
"Six becoming three doesn't create more Americans that want to fly." -Adam Pilarski
 
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longhauler
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Re: Interesting photos of 77Es departing with only MLG retracted.

Thu Jul 12, 2018 12:58 pm

bigb wrote:
In this case, the MLG retracted first then the nose gear started their process of retracting as you can with the doors opening up.

That would be my guess.

It's like a DC-3. If you watch after take-off, one main gear always retracts before the other. If one happened to take a picture right at that moment, it would appear one gear was up and the other down.
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
bigb
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Re: Interesting photos of 77Es departing with only MLG retracted.

Thu Jul 12, 2018 1:00 pm

cloudboy wrote:
I didn't realize you could retract just one set of gear - I thought they all worked in unison.


You can't, but the hydraulic systems and actuators work at different speeds. In this case, the MLG retracted first then the nose gear started their process of retracting as you can with the doors opening up.
 
77H
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Re: Interesting photos of 77Es departing with only MLG retracted.

Thu Jul 12, 2018 1:05 pm

I will hazard a guess that nothing was significantly wrong with either airplane for the simple that most inflight emergencies are well covered on this site and I can’t recall seeing any threads regarding KL or UA 777 flights declaring an emergency as a result gear retraction failures.

77H
 
Newbiepilot
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Re: Interesting photos of 77Es departing with only MLG retracted.

Thu Jul 12, 2018 1:08 pm

bigb wrote:
cloudboy wrote:
I didn't realize you could retract just one set of gear - I thought they all worked in unison.


You can't, but the hydraulic systems and actuators work at different speeds. In this case, the MLG retracted first then the nose gear started their process of retracting as you can with the doors opening up.


In my experience that doesn’t happen with gear retraction on any airplane I have worked on, but I have never done a 777 gear swing. While they don’t move at the same speed, they usually retract at the same time. Main gear doors closed at the same time as nose gear not transiting yet seems a bit odd. Engine out obstacle clearance requirements usually have a set amount of time that the gear must retract in to reduce drag. Each plane is different but it is around 10 seconds to retract after the handle is moved up.

The most common reason for only one gear not retracting is someone forgot to remove the gear pin. Could make sense for UA, but would be surprised if KLM did anything on a turn to justify installing the pin.

Looking at this photo, the nose gear is up before the main gear is up and certainly before main gear doors are closed.

Image

I wonder if there is a deferred hydraulic pump causing the airplane to resequence the gear. There are separated landing gear selector valves that transmit hydraulic fluid to the nose and main gear on the 777. Nose gear uses the electric hydraulic pump and mains use the air driven pump normally, but there is an isolation valve in the system.
 
bigb
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Re: Interesting photos of 77Es departing with only MLG retracted.

Thu Jul 12, 2018 1:40 pm

Newbiepilot wrote:
bigb wrote:
cloudboy wrote:
I didn't realize you could retract just one set of gear - I thought they all worked in unison.


You can't, but the hydraulic systems and actuators work at different speeds. In this case, the MLG retracted first then the nose gear started their process of retracting as you can with the doors opening up.


In my experience that doesn’t happen with gear retraction on any airplane I have worked on, but I have never done a 777 gear swing. While they don’t move at the same speed, they usually retract at the same time. Main gear doors closed at the same time as nose gear not transiting yet seems a bit odd. Engine out obstacle clearance requirements usually have a set amount of time that the gear must retract in to reduce drag. Each plane is different but it is around 10 seconds to retract after the handle is moved up.

The most common reason for only one gear not retracting is someone forgot to remove the gear pin. Could make sense for UA, but would be surprised if KLM did anything on a turn to justify installing the pin.

Looking at this photo, the nose gear is up before the main gear is up and certainly before main gear doors are closed.

Image

I wonder if there is a deferred hydraulic pump causing the airplane to resequence the gear. There are separated landing gear selector valves that transmit hydraulic fluid to the nose and main gear on the 777. Nose gear uses the electric hydraulic pump and mains use the air driven pump normally, but there is an isolation valve in the system.


i agree, all of our landings come up at the same time with the birds I've flown too. But I do those gears were re sequences or just actuators on the nose gear behind the 8 ball.
 
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litz
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Re: Interesting photos of 77Es departing with only MLG retracted.

Fri Jul 13, 2018 1:27 am

77H wrote:
I will hazard a guess that nothing was significantly wrong with either airplane for the simple that most inflight emergencies are well covered on this site and I can’t recall seeing any threads regarding KL or UA 777 flights declaring an emergency as a result gear retraction failures.

77H


Not only would it have been noted on this site, but you can bet VASAviation would have it on YouTube (with full ATC audio) as well.
 
Newbiepilot
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Re: Interesting photos of 77Es departing with only MLG retracted.

Fri Jul 13, 2018 2:02 am

litz wrote:
77H wrote:
I will hazard a guess that nothing was significantly wrong with either airplane for the simple that most inflight emergencies are well covered on this site and I can’t recall seeing any threads regarding KL or UA 777 flights declaring an emergency as a result gear retraction failures.

77H


Not only would it have been noted on this site, but you can bet VASAviation would have it on YouTube (with full ATC audio) as well.


An air turnback due to a gear not retracting wouldn’t get a whole lot of attention. After cycling the gear, the crew would return and it would be barely noticed. If all gear were down and locked after cycling the gear, I don’t believe there is a need to declare an emergency. Incidents like this are fairly common around the world, but twice out of the same airport by the same photographer is what would be unusual.
 
Max Q
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Re: Interesting photos of 77Es departing with only MLG retracted.

Fri Jul 13, 2018 2:53 am

bigb wrote:
cloudboy wrote:
I didn't realize you could retract just one set of gear - I thought they all worked in unison.


You can't, but the hydraulic systems and actuators work at different speeds. In this case, the MLG retracted first then the nose gear started their process of retracting as you can with the doors opening up.




Have to be careful about making absolute statements on this site!


The Convair 880 and 990 could extend the
main gear only at a higher speed than the
nose gear, indeed this procedure was used
as a very effective speedbrake


Further more the DC10 and MD11 could
extend just the wing gear leaving the center bogie retracted, this was not uncommon


I think the A340 series could also leave the
center gear retracted
The best contribution to safety is a competent Pilot.
 
FatCat
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Re: Interesting photos of 77Es departing with only MLG retracted.

Fri Jul 13, 2018 12:59 pm

Max Q wrote:
Have to be careful about making absolute statements on this site!


The Convair 880 and 990 could extend the
main gear only at a higher speed than the
nose gear, indeed this procedure was used
as a very effective speedbrake


Further more the DC10 and MD11 could
extend just the wing gear leaving the center bogie retracted, this was not uncommon


I think the A340 series could also leave the
center gear retracted

Yes both.

During a spotting session at a local airport a very intelligent spotter explained that the hydraulic pumps self regulated the pressures on nose and main landing gear.
I'm not a tech and I don't know if this is true, but seems reasonable to me.
May my post not hurt your feelings

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