All Things Aviation

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Chad Sexington
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Re: All Things Aviation

Post by Chad Sexington »

Brody wrote: Fri Mar 25, 2022 10:40 pm
What is the reasoning behind having the landing gear set up in that way?
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Re: All Things Aviation

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Chad Sexington wrote: Thu Mar 31, 2022 2:38 pm What is the reasoning behind having the landing gear set up in that way?
As an educated guess, I’d say-
Ultimately, redundant mass. The whole thing is more a powered glider, with extended time at high altitude. Every ounce of unnecessary mass is a reduction in performance. It’s a wing, with somewhere to put the human, engine and the cameras.
It needs some minimal landing gear as the airframe is reusable, but landing gear accounts for a very large proportion of total mass within a small unit, and is used for an incredibly small percentage of the total mission.

The drop away gear outriggers weren’t a new idea. The Messerschmitt 163 used a a drop away truck and skid. Some X-planes had very rudimentary gear.
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Re: All Things Aviation

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Freightdog wrote: Thu Mar 31, 2022 6:07 pm
Chad Sexington wrote: Thu Mar 31, 2022 2:38 pm What is the reasoning behind having the landing gear set up in that way?
As an educated guess, I’d say-
Ultimately, redundant mass. The whole thing is more a powered glider, with extended time at high altitude. Every ounce of unnecessary mass is a reduction in performance. It’s a wing, with somewhere to put the human, engine and the cameras.
It needs some minimal landing gear as the airframe is reusable, but landing gear accounts for a very large proportion of total mass within a small unit, and is used for an incredibly small percentage of the total mission.

The drop away gear outriggers weren’t a new idea. The Messerschmitt 163 used a a drop away truck and skid. Some X-planes had very rudimentary gear.
That had crossed my mind, that it was similar to a gliders gear, and that weight was a factor, I just figured it wouldn’t be an issue for a powered aircraft. Interesting.
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Re: All Things Aviation

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Re: All Things Aviation

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Re: All Things Aviation

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Backs it up like a pickup truck.
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Doc67
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Re: All Things Aviation

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I seem to remember an aircraft that did that in snow/slush and filled their engines with crap. This caused the engines to backfire shortly after take-off, destroyed them and bringing down the aircraft. It was on Air Crash Investigation / Mayday series.
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Re: All Things Aviation

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Doc67 wrote: Wed Apr 06, 2022 8:56 am I seem to remember an aircraft that did that in snow/slush and filled their engines with crap. This caused the engines to backfire shortly after take-off, destroyed them and bringing down the aircraft. It was on Air Crash Investigation / Mayday series.
Fascinating series & just when you think they've produced all they can, bang there's more on the horizon. That China crash will be very interesting. RIP
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Re: All Things Aviation

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It’s called, among other terms, power-back. An approved, or at least accepted, manoeuvre for some types, and not for others.

As you mention, doc, the risk of ingestion is a major consideration against it. (Was it the Dulles crash? There was quite a lot wrong with several contamination related accidents)
Even without contamination like snow and ice, the engines can re-ingest exhaust gas, which can result in an engine surge and stall, along with FOD damage, as well.

I believe B757 may be approved under FAA, but not in Europe. Most of the aircraft that I’ve heard of being manoeuvred like this have been tail mounted engine designs, and lighter weight. Like business jets. Whether they’re approved or not, I’ve no idea. You do see and hear of some strange things going on.
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Re: All Things Aviation

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Freightdog wrote: Wed Apr 06, 2022 9:12 am It’s called, among other terms, power-back. An approved, or at least accepted, manoeuvre for some types, and not for others.

As you mention, doc, the risk of ingestion is a major consideration against it. (Was it the Dulles crash? There was quite a lot wrong with several contamination related accidents)
Even without contamination like snow and ice, the engines can re-ingest exhaust gas, which can result in an engine surge and stall, along with FOD damage, as well.

I believe B757 may be approved under FAA, but not in Europe. Most of the aircraft that I’ve heard of being manoeuvred like this have been tail mounted engine designs, and lighter weight. Like business jets. Whether they’re approved or not, I’ve no idea. You do see and hear of some strange things going on.
"surge" is the term I was looking for. I am sure it was the MD rear engine configuration with those big bucket reversers. I can't remember the exact episode, but it was a factor plus the reaction of the crew that finished the engines off. IIRC, when they should have pulled the throttles, they pushed, or maybe the other way round.
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