EVA Air B747 - Abnormal/Emergency Landing TPE

[Weapons_Hot]

A EVA Air B747-F LAX/TPE made an abnormal landing TPE after losing HYD4 system after takeoff LAX.
On arrival TPE, alternate gear extension failed to extend right wing gear.
Airplane landed safely, with no apparent major damage (eg. #3 pod scrape).
CAA are investigating.

[trident3A]

Not if you consider the dihedral, look at this http://www.airliners.net/info/stats.main?id=100

[SLATS_EXTEND]

Originally Posted by SASKATOON9999

If they scraped #3, surely #4 would have to have suffered even worse?

False!

[Intruder]

In NORMAL configuration, the outboard pod of the 747 will hit the ground first. However, the geometry may change without the wing gear extended, since the pivot point will move inboard to the body gear.

[B4MJ]

At preflight #4 pod is higher than #3 pod - factor in the reduced fuel load after a pacific crossing and the #4 pod should be considerably higher than #3.

[Mariner]

I've seen the Air Atlanta 742 that with landed partial gear at SHJ last year. The wing gear didn't come out (it somehow got stuck at its geardoor). They landed at 3 gears, and managed not to scrape a thing, nice job. They had it towed to the ramp. When parked the inboard pod (#3) was very close to the ground. Pod # 4 had much more clearance.

[Captain Airclues]

Weapons_Hot didn't actually say that there was a pod scrape. He said that there was no major damage, for example a #3 pod scrape. He could have been implying that this would have been the most likely damage if there was any, which is a correct statement.

Airclues

[Intruder]

On the 747 the OUTBOARD pod will scrape first! They even teach us that in 747 school!

In a head-on scale drawing of a 747, draw a line that is tangent to the bottoms of the #3 & 4 or #1 & 2 nacelles, extending to below the fuselage. Note that the line intersects the ground at about the centerline of the airplane, well inboard of the same-side landing gear -- the gear that will be the pivot point in a pod strike scenario.

Now draw a line tangent to the bottom of the #1 or #4 pod to the ground at either the same-side wing gear or body gear. Note that the inboard pod is well above this line, regardless of whether you use the wing or body gear.

I've seen the results of several 747 pod strikes. ALL of them were on the outboard pod! For those who claim the inboard will strike first, please show ANY substantiating data!

[Weapons_Hot]

No Apparent Damage

Airclues - you are correct; no reported damage.
Original problem was ruptured hydraulic line. Problem was compounded when alternate extension mode selected and right wing gear failed to extend.
Fault was wing gear uplock motor failed to activate when alternate extension mode selected.
Could have been any number of reasons why it failed.

[Captain Airclues]

Intruder

As you correctly stated in your post of 29th November, the outboard pod will normally strike first, but with the wing gear not extended it will be the inboard. Bring up the frontal view on Tridend3A's post. Now hold a piece of paper under the aircraft on the screen (simulating the ground). Now rotate the piece of paper around the wing gear. The outer pod strikes the paper first. Now rotate the paper around the body gear and you will see that the inner pod strikes the paper first.
I have landed a 747-100 without its wing gear. When we came to a stop the inner pod was about two feet from the runway (managed not to scrape it), whereas the outer pod was slightly higher.

Airclues

[HotDog]

The schematic is not very precise but using the body gear as the pivot point, I still get the impression that the outboard pod will make ground contact first. Maybe I need new glasses.

[Intruder]

Bring up the frontal view on Tridend3A's post. Now hold a piece of paper under the aircraft on the screen (simulating the ground). Now rotate the piece of paper around the wing gear. The outer pod strikes the paper first. Now rotate the paper around the body gear and you will see that the inner pod strikes the paper first.

I did similar measurements with the line drawing in my 747 Flight Handbook. Using that drawing, the inboard pod still clears the ground with the wing gear up. That was the source of my post yesterday.

As I stated earlier, I don't know for sure what happens when the wing gear is up, because I have not seen such a situation. However, we can't tell for sure from the drawings, either, because we don't know if they are to true scale. Also, there will be a significant difference between a normally compressed strut and a collapsed (e.g., during a hard landing) strut.

If Trident3a's pic is based on collapsed struts, and the drawing in my FHB is based on normally extended struts, they may BOTH be "correct"...

So far, it appears that nobody here has actually seen a pod strike with the wing gear up. It could be one of those "it depends" things...

[Longtimer]

Originally Posted by HotDog

The schematic is not very precise but using the body gear as the pivot point, I still get the impression that the outboard pod will make ground contact first. Maybe I need new glasses.

found this pic on the web and from it, it does look like the inboard pod could strike first. But like all web pics, not sure how "real" the picture is.
http://images.google.ca/imgres?imgur...IC:en%26sa%3DN

[Captain Airclues]

When the wing gear fails, the aircraft tilts around a datum line drawn between the good wing gear and the opposite body gear. As well as the lateral tilt there is also a nose down element. As the inboard engine is forward of the gear, this causes the inboard pod to be closer to the ground. It is difficult to demonstrate this using two dimentional drawings. However, if you put an aircraft model on a flat surface with the wing gear over a gap in the surface (didn't want to ruin the model by breaking off the gear) you will see the effect on the pod heights.



Airclues

[HotDog]

Longtimer, your picture is of a total gear up landing situation, in which case the inboard engines will most certainly be closer to the ground than the outboards. However the airplane attitude with one wing gear not extended, will be wing low on the affected side.

[Ozeflyer]

I spoke with the pilot concerned and after the airplane was stopped, the No 4 cowl was far enough off the ground that he could just get his foot under it. No 3 was fine. Airplane was not towed until left wing gear tyres were deflated.
He was told this is the first time that a B744 airplane has not been damaged landing with one wing gear up?

[RatherBeFlying]

As I faintly recall from Davie's 1st edition of Flying the Big Jets where he discussed the then new 747, he suggested landing on the body gear only if one of the wing gear would not come down since the strut on the remaining wing gear would extend all the way.

Is this still so?

[HotDog]

Yes it is. The wing-body gear leveling system tips the airplane away from the extended wing gear. In such a case, the extended wing gear must be retracted and the landing carried out on body gears only, taking care to maintain level lateral attitude and careful slow taxiing.

[jondc9]

it is also true in the third edition of "handling the Big jets".

any pictures of this event? and will someone please verify that both (BOTH) wing gear were retracted for this landing?

[Intruder]

the extended wing gear must be retracted and the landing carried out on body gears only, taking care to maintain level lateral attitude and careful slow taxiing

Not in our 747 Flight handbooks!

They clearly state that we should land using all available gear. besides, there is no way to selectively retract landing gear...