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Soooo..... SwingKid am I to understand from your post it is impossible for a jet to crash while flying at high speed low to the ground?

 

While flying horizontally? Correct, you can't crash. Any pilot can correct me if I'm wrong. This is what makes flying light aircraft so safe - as long as you keep your speed up, you almost need to want to hit the ground, in order to do it. You need to be either in a dive, or at stalling-low speed, to penetrate the air cushion. Trying to approach the ground at high speed in horizontal flight is like trying to push two like magnets ends together. That's how the F-14 started to rise off the ground in the video, without needing to raise its nose.

 

Once you penetrate the ground effect "cushion", either by diving or by stalling, you WILL touch the ground - it's too late then to raise your nose for more lift (see the Su-27UB crash video in another thread). The normal procedure is to do it by stalling, with landing gear extended to land. This is how planes manage to "flare" nose high at the last moment to land - the air cushion holds them aloft until they stall at the last second.

 

Note, none of the above is modelled in Lock On, not even in AFM... There, you can perform such maneuvers as seems to be in this photo without any obstacle, get as close to the ground as you like - but as a result, landings are a bit different than they are in real life. Landing in Lock On is more akin to trapping on a carrier (where there is no ground effect because the deck is elevated). Especially watch the AI on a landing. There is no flare - it approches the runway nose-high from miles away, like a carrier trap, but at dangerously slow speeds. Tying this in real life is very dangerous, because there's no "cushion" up there - fly slow enough to descend with that kind of nose-high pitch, and you are probably going to stall and crash.

 

-SK

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Guest IguanaKing

Someone probably noticed this already...but what's the "thing" on the LH side of the center-line, above the IRST dome? Looks a little elaborate to be a refueling probe. Maybe a ground object that got lost in the edit?

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After looking at the photo I think I see a way to authenticate the photo, or at least determine if the plane was actually that close to the ground. It would not prove that the gear wasn't down at the time, but it would take the search one step further.

 

In the photo there is the small area by the rear ecm boom that looks like it has sky around it. Now while that piece is pretty ambiguous it directs attention elsewhere. In that- if the picture was originally of an aircraft with clear sky behind it then there would also be clear sky on the other side of the cockpit canopy. However there is the taxi way. This means that if the aircraft was in fact somewhere else, that taxiway would need to be fabricated. This also means that the curve of the taxiway line would be an artistic interpritation of what the straight line would look like thru the refraction the canopy creates. However the fact is the amount of image distortion thru the canopy is a mathmatical fact. If one were to look at a similar image of a known valid Su pic they could compare the image distortion- it could possibly be much much less than what we're seeing here. Also if a pic could be found of a Su from a similar vertical angle with a backround at a similar distance away then the angle of curve seen could be empirically compared and more solidly, scientifically, verified.

 

The Defence rests.

 

;)

 

PS- just saw those reverse angle shots, pretty good corraborating evidence

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This coming from a guy who's only flight experience is Lock On? Wow, talk about a wannabe arm-chair expert.

 

Actually, I flew an Cessna (minus takeoff/landing) once and the F-16 sim (including takeoff/landing) at EAFB, Alaska. Regardless, I was right about the last thing Swingkid and I argued about (link available upon request), and I'm right about this.

Dave "Hawg11" St. Jean

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Requesting the link :)

 

http://www.freeweb.hu/f15e/cgi-bin/ikonboard.cgi?;act=ST;f=10;t=51

 

Question by SwingKid:

"F-15C with F100-PW-220 engines, no CFTs, no armament, but full internal fuel. Shouldn't it be able to accelerate like a rocket in a pure vertical climb (even if only slowly)?

 

The engine thrust seems to be greater than the weight of aircraft and full fuel load combined, no? I imagine that in practice, the fule load for "viking" takeoffs might be reduced, to allow a safety margin, but I don't know how much - or if this would actually mean the Eagle can't climb like this with full fuel."

 

Final answer by Yeti (F15E piot):

"...predicting vertical performance is much more complex than simply comparing aircraft weight and rated engine thrust."

Dave "Hawg11" St. Jean

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Guest IguanaKing

Thanks for the info EvilBivol...and Burner...damn you're good. I have to go with real now. I don't like it...but I gotta.

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http://www.freeweb.hu/f15e/cgi-bin/ikonboard.cgi?;act=ST;f=10;t=51

 

Question by SwingKid:

"F-15C with F100-PW-220 engines, no CFTs, no armament, but full internal fuel. Shouldn't it be able to accelerate like a rocket in a pure vertical climb (even if only slowly)?

 

The engine thrust seems to be greater than the weight of aircraft and full fuel load combined, no? I imagine that in practice, the fule load for "viking" takeoffs might be reduced, to allow a safety margin, but I don't know how much - or if this would actually mean the Eagle can't climb like this with full fuel."

 

Final answer by Yeti (F15E piot):

"...predicting vertical performance is much more complex than simply comparing aircraft weight and rated engine thrust."

 

What does any of that have to do with you being "right?"

 

-SK

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Thanks for the info EvilBivol...and Burner...damn you're good. I have to go with real now. I don't like it...but I gotta.

 

:D I got my moments

 

SwingKid- Where did you read about this super ground effect you refer to, sounds like something that would only be covered in an advanced aerodynamics study.

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http://www.freeweb.hu/f15e/cgi-bin/ikonboard.cgi?;act=ST;f=10;t=51

 

Question by SwingKid:

"F-15C with F100-PW-220 engines, no CFTs, no armament, but full internal fuel. Shouldn't it be able to accelerate like a rocket in a pure vertical climb (even if only slowly)?

 

The engine thrust seems to be greater than the weight of aircraft and full fuel load combined, no? I imagine that in practice, the fule load for "viking" takeoffs might be reduced, to allow a safety margin, but I don't know how much - or if this would actually mean the Eagle can't climb like this with full fuel."

 

Final answer by Yeti (F15E piot):

"...predicting vertical performance is much more complex than simply comparing aircraft weight and rated engine thrust."

 

(Real final answer by Yeti): "So I'm saying that although a "clean" F-15 could probably accelerate in the vertical for some distance after takeoff, I have never done it myself and would not be able to verify any details concerning that sort of performance."

 

Quit taking things out of context, or worse, bringing up things that are totally unrelated to the topic (what does a viking climb have to do with ground effect?).

 

One question: did you actually land that Cessna you flew that one time? (the answer is no) So how, logically speaking, can you claim that what has been said about ground effect is untrue if you never even experienced it?

 

[

:D I got my moments

 

SwingKid- Where did you read about this super ground effect you refer to, sounds like something that would only be covered in an advanced aerodynamics study.

 

You've never played Longbow 2 huh? :p

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Guest IguanaKing

 

You've never played Longbow 2 huh? :p

 

It doesn't look to me as if that Flanker is low enough for that. ;)

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It doesn't look to me as if that Flanker is low enough for that. ;)

 

Hmm, maybe. I meant that ground effect is more prominent when flying a helicopter than a jet airplane (due to the mechanisms in which it achieves flight), and that the basics of it are covered in Longbow 2. So you don't necessarily need to go into advanced aerodynamics to be familiar with ground effect.

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SwingKid- Where did you read about this super ground effect you refer to, sounds like something that would only be covered in an advanced aerodynamics study.

 

I learned about it in ground school while studying for a private pilot's license, it's basic aerodynamics in order to make a normal landing with any aircraft AFAIK. It's also described in the landing instructions from the F-15 Dash-1 flight manual.

 

"Most pilots, especially of small aircraft, will experience ground effects on landing; in fact the art of landing largely comes down to understanding when these effects need to be taken into account. As the aircraft descends towards the runway, it will not be affected by ground effect, but as the aircraft flares and descends the last few feet, ground effect will cause a pronounced increase in lift. If not anticipated by the pilot this can cause the aircraft to rise suddenly and significantly — an effect known as a "balloon". Left uncorrected, a balloon can lead to a dangerous situation where the aircraft is rising yet decelerating, a condition which can rapidly lead to a stall, especially when it is considered that landing speeds are generally only a very small margin above the stall speed. A stall even from a few tens of feet above the ground can cause a major, possibly fatal, crash. A balloon may be corrected given sufficient runway remaining, but for novice pilots a better option is to go around. A good landing approach allows for ground effect such that the aircraft flares and is held off in ground effect until it gently descends onto the runway."

 

http://en.wikipedia.org/wiki/Ground_effect

 

Hmm, it seems that it might not apply to a high-speed pass though, since the wingtip vortices are far behind the aircraft in that case...

 

If that photo is real... and it's beginning to seem that it might be... I would not want to be at that airshow. :( I hope it's some kind of illusion.

 

-SK

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Guest IguanaKing
Hmm, maybe. I meant that ground effect is more prominent when flying a helicopter than a jet airplane (due to the mechanisms in which it achieves flight), and that the basics of it are covered in Longbow 2. So you don't necessarily need to go into advanced aerodynamics to be familiar with ground effect.

 

True...no advanced classes needed. It is extremely unlikely that ground effect plays into the current photo though. Even a hecilopter (yes, I intentionally misspelled that...I HATE them) would be hard-pressed to find ground effect at that altitude. He's low...but not that low. ;)

 

Edit...Bublik's photos... now those are getting into ground effect. Gawd that's some impressive stuff!

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What were you even right about? Nobody proved that the F-15C can or cannot accelerate vertically. You can't compare it with the Mudhen because it has like twice the thrust-to-weight ratio and much less drag in any case.

 

Setting that OT aside, it looks like he might be right in this case anyway.

 

I actually like being proven wrong. Look at it this way - no more Russian-flown airshows for me. He might have just saved my life.

 

-SK

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It is extremely unlikely that ground effect plays into the current photo though. Even a hecilopter (yes, I intentionally misspelled that...I HATE them) would be hard-pressed to find ground effect at that altitude. He's low...but not that low. ;)

 

"on a fixed-wing monoplane, about half the distance from a wingtip to the fuselage."

 

If he's low enough to touch the ground with wheels extended, he's below the ground effect.

 

-SK

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