Warbird Information Exchange

Hello all,

I am not sure if this, which relates to modern military aircraft, belongs here.

A recent short piece on CC.com concerns the new Chinese cargo transport:

http://www.cnn.com/videos/world/2016/07/07/china-military-plane-y-20-orig.cnn

How does this compare to other modern aircraft (AMerican and Russian).

This subject is well outside my general, more vintage, interest, but I am curious thought to float the question here.

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Kevin McCartney

Looks like a pretty good copy of the Kawasaki C-1. But since that design is at best 40 years old I'd suggest the Y-20 is similarly obsolete.

Maybe, but aerodynamics haven't changed significantly in 40 years. Yeah, we have winglets and a couple of other things that add a little efficiency, but that's in the margins, rather than center cut. The bigger question, IMO, is the engines and whether the Chinese have enough experience (or bought enough expertise) to deal with an airplane that large and the abuse it will be subject to in military use.

In other words, it is one thing to build a big 'ol military transport. Making it work and last over the long haul is another issue.

It looks most like an Ilyushin Il-76. Quite similar in terms of weights, span, wing are etc. There have been Il-76s in China for decades, so I am sure they were familiar with that. The C-141 is quite similar as well. The Mitsubishi is smaller and only has 2 engines.

Not surprising what it looks like. Similar requirements for a modern 4 jet engine military aircraft, with a drive on rear ramp, are almost always going to end up looking similar. Common characteristics are a high wing of moderate sweep, lots of flap area, side sponsons so the landing gear does not compromise the cargo deck, main wing spar above the cargo deck, and a high T tail being used by most. The high T tail avoids the horizontal stabilizers being washed out by the wing.

Although the shape is similar, it does sound like they are making the most of modern composite designs. China has indeed come a long way.

T tails led to deep stalls and fatal crashes ( the well known crash of a BAC 1-11 and HS Trident during stall tests) in the 60s, so I'm not sure I can agree with you.
As I understand it, that led to stick shakers and other aids.

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Remember the vets, the wonderful planes they flew and their sacrifices for a future many of them did not live to see.
Note political free signature.
I figure if you wanted my opinion on items unrelated to this forum, you'd ask for it.

That was before the behavior of the T-Tail design was fully understood. Since the BAC 1-11 and VC-10, T-tails have typically been more stall resistant than standard tails because of not only the systems introduced, but also because of changes to how the wing is constructed to introduce a pitch down moment prior to entering too deep of a stall where the issues of a "deep stall" would become a problem. I'm not aware of any "deep stall" crashes that have occurred with any of the 2nd or 3rd generation T-Tail aircraft and it's becoming more and more common of aircraft to have them, including several designs changing from a cruciform tail to a T-Tail (the Gulfstream G280 being most recent).

Take a bag, shake up the A400M, C-17, and C-141 and you have the Chinese airplane. Its real strength will be determined by engines, low speed characteristics, and materials engineering. Oh, and the video shows that they have mastered the fine art of aiming water cannon.

Ken

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"Take care of the little things and the big things will take care of themselves."

Ken, put in a bag as in "Shake and Bake" fried chicken ? A friend of mine was a "Shake and Bake" NCO during the Vietnam war. He was drafted and after finishing training was assigned to a sleepy little outpost in Georgia. He thought I got it made the next two years". Six months into his conscription he was promoted to Sergeant E-5 because of his high test scores. And of course orders to report to a Huey squadron going to Vietnam.
Gotta love that Shake and Bake concept!

If I remember correctly the 'deep stall' phenomena of the 60's wasn't just about having a T tail.

It was the combination of the T tail and the rear-mounted engines. This combination was the real killer.

Funny how the fashion for rear-mounted engines on large aircraft has all but died out.

We must be learning a thing or two along the way.

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Little Johnny : "When I grow up I want to be a pilot!"

Johnny's Mother : "Don't be silly Dear - you can't do both!"

I'm no Burt Rutan, but I don't recall the tail mounted engines being the problem.
The DC-9 and 727 never had deep stall issues...they're the same generation as the BAC 1-11 and Trident.
A deep stall means the wing blankets the elevators at high angle of attack, I'm not sure engine placement could effect that.

And aside from the VC-10 and IL-62, I can't think of any larger airliners that ever had rear engines. The switch to Wing mounted engines began with the 707, remember the Comet and the UK "V" bombers and Soviet airliners/bombers had engines in the wing root.
And since then, various regional jet airliners and most bizjet have had rear engines....

_________________
Remember the vets, the wonderful planes they flew and their sacrifices for a future many of them did not live to see.
Note political free signature.
I figure if you wanted my opinion on items unrelated to this forum, you'd ask for it.

Not to be argumentative but the MD-80, MD-90, & 717 series does suffer from some deep stall quirks. (I flew the DC-9 but don't recall offhand its specifics) Although the elevators are free-floating and tab-controlled, a push of the column to full forward activates a hydraulically powered elevator to assist in deep stall recovery. I did not fly the MD-90 specifically, but I have seen the pivots on the trailing edge of the engine pylons designed to assist in stall recovery as well, as they activate during the taxi control checks.

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"Take care of the little things and the big things will take care of themselves."

I suspect the main differences are fuel efficiency and systems.

With a large number of aircraft (like in the USAF C-17 fleet), even a few percent reduction in drag leads to a huge overall fuel savings.

With respect to the systems, can the Y-20 do a precision airdrop? Can it do aeromedical missions?

What will the dispatch reliability be of the Y-20? A great performing airplane with a 40% dispatch reliability rate isn't very useful.

Seems like these are all things that can be discovered and addressed during flight testing and FAA certification. This may not have been discovered in the first generation aircraft, but now that it is well known I would expect the testing would have smoked this stuff out as it apparently was in the MD-90. Modern transports also have the benefit of fly-by-wire computer assisted flight controls to keep aircraft out of these flight regimes.