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McDonnell-Douglas Model 226 "Quiet Attack Aircraft" : Early Naval Stealth study

hesham

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Hi,

I want to know the McDonnell Douglas XST proposal,that because the USAF
in 1975 awarded the contracts,to Northrop and MD,but there was a private
venture from Lockheed,did we speak about this proposal before ?.
 

flateric

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We did. It wasn't XST. It was Quiet Attack Aircraft

DEVELOPMENT OF THE F-117 NIGHTHAWK
As a follow-up to Harvey and other research programs, DARPA sent out RFPs for
competitive study contracts to Northrop, McDonnell-Douglas, General
Dynamics, Fairchild, and Grumman in 1974 to develop design concepts for a
very low RCS combat aircraft.11 Only the first three firms responded. Lockheed
also soon joined the competition.12 Its engineers developed a highly
unconventional faceted design nicknamed the “Hopeless Diamond,” which
contained only two-dimensional flat surfaces. This was because RCS could only
be calculated with high precision for two-dimensional surfaces given the state
of knowledge and the capability of computers at the time. Northrop proposed a
more conventional delta-wing stealth design with the air inlet on top, which
used a combination of angular and rounded surfaces.13 McDonnell proposed a
variant of its “Quiet Attack” aircraft design that had been developed earlier
under a contract for the Office of Naval Research. DARPA soon realized that
both Lockheed and Northrop had proposed design concepts that were
revolutionary in their potential to reduce RCS. In October, DARPA awarded
these two companies follow-on contracts to develop their design concepts
further. The two companies built models of their designs, which engineers then
tested in early 1976 on a fixed pole in a competitive “fly-off” at the Air Force’s
radar range in New Mexico. In April, DARPA informed Lockheed that it had
won the competition.


Scott builds a master for it of it - just in case http://www.up-ship.com/models/stealth2.htm
 

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AeroFranz

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In the XP-67 case, the blending was done for purely aerodynamical considerations, I think.
Here, it was thought that continuously curving surfaces would be better in terms of RCS.
 

OM

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Just call me Ray said:
...is it merely "coincidental" that McDonnell was also responsible for the XP-67 Moonbat? :)

...Oh, so *they're* the ones responsible for Moonbat :p :p :p
 

Just call me Ray

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According to a post at Above Top Secret (here: http://www.abovetopsecret.com/forum/thread202776/pg1 ) the prototype XST was buried in the desert with "other black programs," and was slated to be unearthed and restored but it has since been misplaced.

I don't think there's any real reason to believe this though.
 

quellish

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Just call me Ray said:
According to a post at Above Top Secret (here: http://www.abovetopsecret.com/forum/thread202776/pg1 ) the prototype XST was buried in the desert with "other black programs," and was slated to be unearthed and restored but it has since been misplaced.

I don't think there's any real reason to believe this though.

Unlike most posts on that board, that one originally comes from a very reputable source.

What is really interesting is that Lockeed was also working on a LO project for the Navy at the same time McD was working on the Quiet study. Wether they were part of the same program I do not know, but it was this work that eventually lead to ECHO 1. Lockheed was still working from their successes with the Blackbird and D-21 program, while later the ECHO1 tools allowed them to leap beyond that.
 

XP67_Moonbat

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What type of exhaust was planned for the McDonnell bird. The aft end isn't too clearly defined.
 

AeroFranz

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Apart from being new to me, these McAir artist's drawings Mark unearthed are quite beautiful. I can't believe they never achieved widespread distribution.
 

overscan (PaulMM)

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Quiet Attack Specs:

Length : 44.6 ft
Span: 56.5 ft
Takeoff weight: 14,410lb
Empty weight: 9,960lb
Fuel : 3415lb
Wing area: 400 sq ft
Aspect ratio: 8
Takeoff thrust/weight ratio: 0.44
Quiet speed, 2500ft altitude: 112kn
Max speed, 2500ft altitude: 400kn

High-bypass, tip driven turbofan
Plug nozzle

Source: Have Blue and the F-117A: evolution of the "Stealth Fighter" By David C. Aronstein, Albert C. Piccirillo
 

AeroFranz

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Similar to Ryan XV-5, except the fan is positioned upright for propulsion, as opposed to flat for lift.
Basically you have a gas generator, whose exhaust is channeled into a scroll surrounding a fan, and impinging on a tip turbine stage concentric to said fan. The gas generator and the fan need not be close together, as you can duct the exhaust quite a ways, but you then incur duct losses.
I believe the interest in this particular case might have been to achieve a diluted exhaust temperature for signature purposes.
 

jzichek

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Just posted an article on this aircraft study at RetroMechanix.com, along with 8 images:

5667648998_c8637f713e_o.jpg


The article features some CG artwork I did several years back. Special thanks to Mark Nankivil for letting me post the contemporary artist's impression from the Greater St. Louis Air & Space Museum. I believe the article presents information that has not been published before, so please check it out when you have a moment.
 

SOC

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Really interesting article!
 

AeroFranz

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Great work. Really interesting read. Can't wait for the next article :)
 

Stargazer2006

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Thanks Jared for this great article and fantastic graphics. You've really made this project stand out!

I still wonder what ties existed between the McDonnell Model 226 program and the "Marshmallow" design that shares some design similarities with it. Any ideas?
 

fightingirish

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...Lt. Cmdr. Tom "Iceman" Kazansky.... :D ;D


Great Article so far!!!
 

Pioneer

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Wow Jared jzichek
I love your site and love your CGI work ;D

Keep it up!!

Any sneak peak of what else you have lined up?

Regards
Pioneer
 

overscan (PaulMM)

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Stargazer2006 said:
Thanks Jared for this great article and fantastic graphics. You've really made this project stand out!

I still wonder what ties existed between the McDonnell Model 226 program and the "Marshmallow" design that shares some design similarities with it. Any ideas?

"Marshmallow" was a fictitious design used to represent General Dynamics' "stealthy" ATF concept, as the Sneaky Pete/HAVE KEY derived design was classified. It is unlikely to have any direct relation to Model 226 unless the artist who drew it was aware of the 226 design and used it as inspiration. It conforms to the typical idea of stealth pre-F-117 and has similarities to Quiet Bird, and the Rockwell Flying Banana...

Marshmallow
index.php


Quiet Bird
index.php


Flying Banana
index.php
 

jzichek

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Re: McDonnell-Douglas Model 226 "Quiet Attack Aircraft": Early Naval Stealth

Thanks for the kinds words all! I'm not entirely sure of the relationship between the McDonnell Douglas QAA and the other studies mentioned; hopefully more information will come to light in the years ahead, but it may be a while...
 

AeroFranz

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if it helps, i sent the link to your article to two people who worked on the "flying banana" and the "surprise fighter", both contemporary studies from other companies. Maybe they can weigh in with additional details.
 

Stargazer2006

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Hmmm... interesting, overscan, thanks. I must admit that the "Flying Banana" is new to me. Any idea what company did that study?
 

AeroFranz

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I got a reply from Dave Hall, the designer of the "Flying Banana"

My Rockwell study was for ONR from June 1971 to October 1973 and was focused on simultaneously minimizing radar, infrared, acoustic, and visual signatures at the expense of performance and even utility in order to set an upper or lower bound on what the answer had to be. The threat was SA-2 and SA-3 SAMs and, specifically, their metric wavelength radars. As the study wound down, ONR offered Rockwell a sole-source follow-on which the division president turned down to focus on augmenter wing VTOL. His exact phrase was "we're putting all our eggs in one basket". ONR begged us to build scale models to fly against the U.S. russian radar site and he said no. We did the flying banana for a combination of this later study that McDAC got and an AF bid opportunity before being told to no-bid unless there was an augmenter involved.

also see "silent night" design. Some of its background is retold on this page:
http://www.fantastic-plastic.com/SilentStealthCatalogPage.htm
 

Grey Havoc

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AeroFranz said:
As the study wound down, ONR offered Rockwell a sole-source follow-on which the division president turned down to focus on augmenter wing VTOL. His exact phrase was "we're putting all our eggs in one basket". ONR begged us to build scale models to fly against the U.S. russian radar site and he said no. We did the flying banana for a combination of this later study that McDAC got and an AF bid opportunity before being told to no-bid unless there was an augmenter involved.

What the heck was that president smoking?!!!
 

hesham

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Hi,


here is from the book; Warbird Tech; Lockheed-Martin F-117 Nighthawk,a drawing
to McDonnell-Douglas Quiet Attack aircraft,but differ in rear fuselage,please compare
the drawings.
 

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Avimimus

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AeroFranz said:
Similar to Ryan XV-5, except the fan is positioned upright for propulsion, as opposed to flat for lift.
Basically you have a gas generator, whose exhaust is channeled into a scroll surrounding a fan, and impinging on a tip turbine stage concentric to said fan. The gas generator and the fan need not be close together, as you can duct the exhaust quite a ways, but you then incur duct losses.
I believe the interest in this particular case might have been to achieve a diluted exhaust temperature for signature purposes.

Quite interesting! It could also increase cruise efficiency - correct? It would effectively increase the bypass?
 

AeroFranz

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It does. Whether it is enough to recoup the other penalties remains to be seen. Because of the added thickness of the scroll duct, the bypass duct itself grows in diameter and increases aerodynamic drag. This is often cited as one of the limiting factors in the growth of bypass ratio of conventional turbofans (among other things).
Then you have to factor how efficiently the 'fluid' transmission coupling through the tip turbine works compared to a more traditional turbofan.
 

NoiseMaker

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"Basically you have a gas generator, whose exhaust is channeled into a scroll surrounding a fan, and impinging on a tip turbine stage concentric to said fan. The gas generator and the fan need not be close together, as you can duct the exhaust quite a ways, but you then incur duct losses.
I believe the interest in this particular case might have been to achieve a diluted exhaust temperature for signature purposes. "


As stated, the tip fans were driven by the exhaust from small turbojet gas generators. The center portion of the tip fan accelerated the airflow from the inlet out the exhaust. An "inside-out" turbofan, if you will. It wasn't very fuel efficient at all, since the turbojet had to run at high throttle settings all the time to produce the airflow for the tip blades. Aircraft acceleration and maneuverability were poor as well, since there was little to no "excess" thrust and poor response to throttle movement. Think along the lines of a P-80 with about half the thrust...

The final report on this design was written in 1972, and is still classified SECRET. The Office of Naval Research refuses to declassify the entire report because no current ONR office can trace lineage back to the office that paid McDonnell Douglas to do this design. And, of course, none of the people are around, either. Took me 4 years just to get the 3-view drawings in that report declassified... and they were only CONFIDENTIAL...

Payload was just a couple of bombs in a centerline bomb bay. No air-to-air stuff at all.

To my knowledge, when the report was delivered, all work on the design stopped. No wind tunnel models, no RCS models etc. were ever built. Everything was theoretical calculations. RCS was very new stuff back then, and everyone was learning on the fly. It would be interesting to build a proper RCS model and test it to see just how far off those 1972 predictions were...

The upper two designs in RetroMechanix drawing 3 are not related to the Quiet Attack aircraft. They were rejected designs from the A-X study years eariler that (after several iterations) eventually became the A-10. The McAir (this preceded the merger with Douglas in 1967!) design that was submitted looked a lot like the German Ta-154 Moskito - a high wing, twin turboprop...
 

quellish

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PaulMM (Overscan) said:
Great info, thanks a lot.

From 1971 to 1975 Boeing was contracted by ONR (N00014-71-C-207/NR, N00014-72-C-0303/NR) as well to study low RCS fighter/attack aircraft. These seem to have been part of the same group of studies that also resulted in the Model 226. Boeing's work built on the earlier Quiet Bird, SRAM, and other projects. The Boeing approach had a greater degree of experience and maturity behind it vs. the McDD approach, unfortunately (foreshadowing!) USN as an organization didn't quite *get* that LO isn't all aspect or nothing.
 

overscan (PaulMM)

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NoiseMaker said:
The upper two designs in RetroMechanix drawing 3 are not related to the Quiet Attack aircraft. They were rejected designs from the A-X study years eariler that (after several iterations) eventually became the A-10. The McAir (this preceded the merger with Douglas in 1967!) design that was submitted looked a lot like the German Ta-154 Moskito - a high wing, twin turboprop...


You mean this:
mcdonnell-douglas-ax-gif.166644

 
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NoiseMaker

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Yep. That's it. There were multiple nose options (recce, for example), multiple armament options (number of wing pylons), and even two turboprop engine options. Overall performance wasn't bad for that era, but they didn't believe the USAF would follow through on the "jet-only" comments and reject all propeller driven designs. The A-9 vs A-10 contest was the result... I never understood why Grumman didn't offer turboprop F7F Tigercats (other than USN vs USAF rivalry), because that's essentially what this is....
 

hesham

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Hi,

did we send these two drawings before in the forum generally ?,I can't
find them !.

Clearly it was from RetroMechanix site.


 

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