Monday, September 21, 2015

The .22

So, There I was….* Last Tuesday morning, reading Tuna’s post wondering what it was that the Russians almost ruined whilst simultaneously looking at hideous aircraft pron.  But, hey, when you’re so ground bound that you’re forced to jealously read other folks’ account of just taking off and flying around West Virginia for the fun of it, or reading about the pre-solo flight training of a soon to be pilot, then who am I  to criticize an aircraft based on looks alone.

In any case, Tuna commented that one of the aircraft looked like it had been “designed in a vineyard, or at least after a few glasses of vino.”  Having tipped a few glasses of vino in my day, I quickly saw the resemblance and since he said it was a French plane, the possibility that his statement is totally accurate I’d say is high. 
Hard to get a feel for size, but the glass area between the nose and the intake is the cockpit, so large enough to seat a person.
Source

So, I read through the rest of the post and made one of my usual pithy comments, then scrolled back through to the French Leduc .22.  Something bugged me about it and I couldn’t figure out what it was.  I studied the picture, but it was still eluding me.  Ctrl-C, Ctrl-V the name into Google and off we go. (USAF Birthday last week, had to do it)
The Leduc .22. Look at how the cockpit is arranged.  Here is a better picture of it.  Source

Anyhow, there’s the usual Wikipedia article, which following Suldog’s guidance, I read for background and links to other good sources.  Not a lot of info in the 4 sentences provided and the only web link is to a web page in French.  One of the bits of information mentioned that it was a ramjet. Knowing that the USAF is still perfecting Ramjet technology, this piqued my interest and I dug a little deeper. 

Cutting and pasting the French Web Page into Google Translate, (not wishing to impose on Sarge’s French translation skills on his day off), gave me some key pieces of information. 
The two portals on the front are where the pilot sits.  Not sure how (if?) he'd have gotten out in an emergency.
Source

Evidently Rene' Leduc had begun to build a prototype in the 30s and had actually gotten it to fly, albeit after the war.  (Surprisingly, This article says he was able to keep the Germans in the dark about his work on ramjets. )

The Leduc .10
Source

Because a ramjet provides no thrust unless air is moving through it, the .10 required  a lift and dropoff to fly.  The.22 was fitted with a conventional jet engine as well as the ramjet, so could actually take off on its own power.
Source
All 4 prototypes (6 aircraft) flew successfully, although during testing the second and third were destroyed in accidents and the pilots severely injured.  The final prototype,the one on Tuna’s page, flew first on Dec 26, 1956.  It flew 34 times before they attempted lighting the ramjet.  The ramjet successfully lit, but failed to achieve the speed of sound. Subsequent flights experienced the same problem, and the program, which was intended to produce a  supersonic fighter, was eventually cancelled.
Source


At that point, I knew what it was about the picture that bugged me.  It didn't have Whitcomb’s area rule pinch.  Richard Whitcomb, in 1952, had been working at the Langley Research Center and published a paper outlining how to overcome the drag that built up along the fuselage of an aircraft as it approached the speed of sound.  It involved reducing the size of the fuselage in the area where the wing is attached.  Since most jet engines at the time were comparatively low powered, they could not easily get through the sound barrier.

By “pinching” the fuselage, there isn't an abrupt increase in the total surface area of the aircraft being pushed through the sky. The buildup of drag as the supersonic shockwave made its way down the aircraft was reduced.  And reduction in drag is almost always a good thing in the flying world.

Clearly, Leduc’s would-be supersonic fighter would have benefited from a pinch in the waste.  As I pondered that, I remembered that both the T-38 and the F-4 had that feature.
You can see the area rule adjustment right where the US Air Force is on the side
(USAF Photo)





You can also see it here starting at the intake and becoming very pronounced at the bump between the green and brown paint.
(USAF Photo)

 However, I didn’t remember it on the F-15. Had they done away with it? The Pratt and Whitney engines were certainly powerful enough.  Yet, the F-4 was the epitome of the saying, “with enough power, even a brick will fly”.  If McDonnell Douglas engineers had decided it was worth it for the F-4, I didn’t believe they would forsake it on the Eagle.

So, I’m reading about Area Rule, and come upon a forum that had a thread about it and why modern fighters didn’t have the pinch.  Most of the commenters said it was because of “so much thrust”.  One of the commenters however said that one of the reasons the 747 was so efficient was that the designers had taken Area Rule into account, and rather than pinch the fuselage which would reduce interior seating space, they had built the now famous 747 bump.  
Wikipedia


This picture shows that the bump ends almost exactly where the wings begin.

Which got me to thinking about the F-15.
(NASA.Gov Photo)

As I’m looking at pictures of the F-15, I thought I had figured out how the engineers had done it with this picture.

And knew I did with this one.
Loaded for bear!
(Commons.wikimedia)

Clever those McD Engineers. Building the canopy, engine bays, wing roots and nacelles to not only have outstanding visibility, hold the engines, and provide lift all while reducing drag.

For those of you that would like to see the Leduc .22 in flight, I present this.  Hopefully you are fluent in Spanish.

*SJC

21 comments:

  1. Fascinating topic and a great post. I remember reading about the F-102 in grade school, my first inkling that "looks really cool" just isn't a criteria that nature cares about. It's ironic that Leduc et al. had to finely tune the aerodynamics of the air flow/gas path on the inside to produce a working ramjet but seemingly neglected the external aerodynamics.

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    1. Especially, since the NACA paper had been published prior to this model beginning development. Engineering Limitations or Financial Limitations? I'm suspecting the latter. I'm not an engineer, nor have I played one on TV, but the diagrams in the Whitcomb link showed the efficiency gain with the 102 were not all that outstanding. They may have just got lucky. Doing the necessary calculations in 1952 meant Slide Rule, so Time. And time = money.

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    2. That's a very good point. Aircraft design used to originate mainly in the private sector where both small and large companies were perpetually strapped for cash. I'm not sure that today's model, where nod-nod-wink-wink "private" companies are awash in government money but still struggle to fund the actual design and development of aircraft, is much of an improvement. But that's just me.

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    3. I don't know. The 15, 16, 17/18 and 22 appear to all be well designed, capable aircraft. AFAIC the jury's still way out on the 21st century's version of the Aardvark.

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    4. Ah, I wasn't clear (surprise?). The jets are superb including the 35 (you seem to have overlooked the best of the lot, the 14) , not perfect but certainly SOTA. My mislaid point is the financial one. The cost of every jet since 1980 includes braces, college, vacations, portfolios, second homes, seventh cars, etc.

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    5. This comment has been removed by the author.

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  2. I had to head over to NASA's website to attempt to comprehend the whats, whys and hows of a ramjet.

    Simpler and lighter, good for maintenance, good for limiting aircraft weight.

    Can't produce thrust if it's not moving. Well, alrighty then. Which made me ask, "And the point would be?"

    But ya know, SCIENCE! People investigate stuff to see if it's feasible, at least that's what we use to do. If it's not feasible we used to move on. (Pretty sure the PC "scientists" avoid that like the plague. Now it's all about harvesting tax dollars.)

    Interesting post Juvat and what a weird looking aircraft.

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    1. Good point. It's one of those things I've always wondered about. What was the First Guy thinking? When I was a kid and "the agony of defeat" was playing on Saturdays, I remember wondering, who was the first guy that thought about ski jumping and what was he thinking when he went off the end? Similarly, what was the first test pilot, sitting in the cockpit with a HUGE engine behind him and no easy way to get out of the airplane, thinking when the lift vehicle nosed over and released the clamps. Gee, I hope it lights?

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    2. Pilote D'essai performs the classic Gallic Shrug.

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    3. Before or after he hit the ground?

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  3. I learned about the "WASP" profile from a TIME/LIFE science book on Flight published in the mid 60's. I still have the book though it's in rough shape. There was a great shot from 12 0'clock high of the F-102's shapely figure. The X-1's profile must have been overcome by the rocket thrust.

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    1. I think you're right on the brute force model. The Hun had the same issue, but was able to get to mach 1 in level flight. I don't think it got too much beyond though.

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    2. If memory serves, the X-1 shape was modeled after the .50 cal round.

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    3. Did not know that. Interesting.

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  4. Don't frget the Republic F-105 fir that pinched-waist "coke bottle" shape. It helped make that thing MOVE!

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  5. Yeah, go right ahead and fly that one- I'll be over here with the camera and insurance policy... :-)

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    1. I think I'd have passed on flying that one.

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    2. I had a ride in the TF105 (or was it the 105F?) once. It was a little shaky at altitude, but what a rock at 500K at 100'.

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    3. We had an exercise on the Eglin range when I was at Moody. The last Guard squadron with F-105Fs was there also. We were on a little Hunter Killer with a single 105. He was out front and we were line abreast behind. We were having a hard time maintaining formation as we were always getting too close. So, I asked him to push it up. That was the last time I saw him until debrief. What a rocket!

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  6. Wasn't the Navy's F11F Tiger the first fighter to use area rule? Or was it just the first Naval aircraft to do so? Can't recall if the 102 came into service before it or not..

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    1. It definitely was the first Navy aircraft, but doing research for this article, I only saw one reference to it in discussions of area rule. Every other one talked about the 102, which definitely was the first USAF aircraft.

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