Now THAT's an airplane, part deux

I've read that because the US dollar is so weak, airplane purchasers are purchasing mainly boeing which in return is reeking havoc on airbus's employment.

 

Reserecting an old thread,
I missed this big beasty when it came to Adelaide, TWICE!! How can that be?

I find it hard to believe that an aircraft that big can be built and that it gets off the ground.

 

Re: Now THAT's an airplane, part deux

 

Re: Now THAT's an airplane, part deux

 

Wth are those sparks?

 

Re: Now THAT's an airplane, part deux

If its anything like the equivalent Boeing tests for which I saw video decades ago, they bolted a skid to the underside of the tail, and intentionally dragged it a ways down the runway. Minimum takeoff speed is probably determined by the tail hitting the ground just as the main wheels lift off.

 

Re: Now THAT's an airplane, part deux

Yep. On this note, Boeing news | Tough testing awaits the Boeing 787 Dreamliner once it takes to the air | Seattle Times Newspaper talks about some of the tests that commercial airlines have to go through in order to get FAA certification.

I saw a documentary on the 777 many years ago (wish it was being rerun and more widely available for rent) that showed a bunch of tests including the high speed aborted takeoff one. IIRC, there was one Airbus plane where the aborted takeoff test ended very badly w/exploding tires and the firefighters having insufficient water.

 

Re: Now THAT's an airplane, part deux

No, none of my family were there.

 

Re: Now THAT's an airplane, part deux

And sometimes the tail scrapes with people on board!!!

Pilot error confirmed as cause of Melbourne accident - The National Newspaper

What's a hundred tonnes between friends?

 

Re: Now THAT's an airplane, part deux

What's a hundred tonnes extra on a trip from Melborne to Dubai in terms of fuel consumption? Better be doing some serious Hipermileing there!!!!

 

Re: Now THAT's an airplane, part deux

Doesn't this belong in the online dating thread?

 

Some more A380 pix:

 

Re: Now THAT's an airplane, part deux

They were doing a test that determines "minimum unstick" speed. It's a test that is done for certification and the tail of the aircraft drags on the runway when it is accomplished.

 

Re: Now THAT's an airplane, part deux

This is part of the certification test, the Vmu takeoff speed

Vmu = Velocity / minimum unstick

What that means is the minimum velocity the aircraft will struggle into the air without a proper rotate past V2/Vr speed. With flaps set for takeoff speed, the takeoff roll is much longer than usual, and the aircraft is dangerously at the stall boundary

An application for this test is if the flight crew noticed something on the runway, eg a large animal or another aircraft, and was already past V1. They would force the aircraft into the air before the safe V2 speed is reached, which will very likely cause severe damage to the underside of the tail

 

Re: Now THAT's an airplane, part deux

Actually jayman, I'd agree with your first couple of sentences. It's simply a certification speed used to compute other speeds (like Vlof and ultimately V2). All they do is rotate the airplane to the maximum pitch the aircraft can achieve with its mains in the ground, causing the tail to strike the runway. I would assume they would begin rotation to maximum pitch attitude at Vr, but I'm not sure what the test pilots have to do for certification purposes. When the aircraft lifts off, they have their Vmu speed. Beyond that, there is no practical application for Vmu speed. We don't compute Vmu for takeoff, nor is it noted anywhere in our manuals other than in theoretical takeoff performance discussion.

And at Vmu, the aircraft is above stall speed by some safe margin. In fact, Vmu occurs at a speed that is above Vr, which is already a safe rotation speed, and is the speed at which we would begin normal takeoff rotation. Also, to clarify, unless V1/Vr/V2 are the same (possible I guess on some transport category aircraft), we are already rotating before V2 and at a "safe" speed, with "safe" being a relative term.

God help the animal we hit at V1. Instant hamburger!!

 

Re: Now THAT's an airplane, part deux

Not a total loss - lunch for the ground crew?

 

Forgot to post this:


Antonov An-225 - Wikipedia, the free encyclopedia

 

Re: Now THAT's an airplane, part deux

I'm getting to the point of getting bored with the A380. Over the last three months, I have spent nearly every weekend flying somewhere in Asia. 75% of the time I have been in an A380, both Singapore Airlines and Qantas. Flown both upper deck and lower deck - Singapore Airlines have a section in the upper deck for economy passengers (definitely my favourite section when flying Singapore) while Qantas has put first, business and premium economy on the upper and the whole of the lower deck is standard economy. So far, Qantas have upgraded me every time, so I still do not know what Qantas's lower deck is like, but doubt that it is much worse or better than a 747.

Generally see two or three of them in Sydney at any time - they have had to put in new gates - the quickest and best way to load everyone on board is to have two or three air bridges - one to the upper deck. Sydney only has two air bridges for each of the A380 gates - Singapore has a couple with three air bridges.

 

Re: Now THAT's an airplane, part deux

Well, I didn't want to get too technical about it, but ....

Minimum Unstick (VMU) Speed Margin

Again, in the real world, there is little practical value to this sort of maneuver. If performed, you have to assume significant damage to the aircraft. I witnessed one such Vmu certification test, really couldn't understand the practical value

Incidentally, it was an accidental tail strike on landing, which cracked the rear pressure bulkhead, improperly repaired by Boeing, that caused the explosive decompression and loss of that JAL 123 flight in Japan. The entire tail blew off, which destroyed all 3 hydraulic systems, leaving the 747 uncontrollable