• Hi Guest! Forum rules have been updated. All users please read here.

Douglas Model 671 and 684 (aka "D-558-III") X Planes

Maveric

Fight for yor Right!
Joined
Jan 14, 2007
Messages
1,987
Reaction score
346
Hi all,

there is a drawing of Douglas X-planes. I believe the D.558-III "Skyflash" is the Douglas D.684?

Servus Maveric
 

Attachments

  • douglas.jpg
    douglas.jpg
    508.4 KB · Views: 1,055

archipeppe

ACCESS: Top Secret
Joined
Oct 18, 2007
Messages
1,712
Reaction score
362
Maveric said:
I believe the D.558-III "Skyflash" is the Douglas D.684?

Yes it is.
It was conceived as concurrent for the X 15 original proposal, won (at least) by NAA ESO 7487.

I enclose my personal contribution in matter.
 

Attachments

  • D558-3.jpg
    D558-3.jpg
    167.5 KB · Views: 849

Tailspin Turtle

ACCESS: Top Secret
Senior Member
Joined
Dec 6, 2007
Messages
697
Reaction score
84
Website
www.tommythomason.com
My diatribe on the subject:

D-558-3?

“D-558-3” is commonly used to identify the proposed Douglas hypersonic research aircraft follow-on to their successful D-558-1 Skystreak and D-558-2 Skyrocket program. Although the designation doesn’t officially exist, that hasn’t hindered its use by aviation historians and others to refer to two somewhat different Douglas designs, the Model 671 and 684. What’s more, the name “Skyflash” is sometimes used in conjunction with the D-558-3 designation but appears to have even less validity.

The original D-558 type name came from the Navy’s practice in the 1940s for identifying aircraft types that they procured for purely experimental reasons and that did not already have a military or civil type identification. In those cases, the Navy simply gave the aircraft a designation that combined the Navy’s letter for the manufacturer with the manufacturer’s internal model number for the design.

For example, the Vought skimmer demonstrator for the F5U program was the V-173 and the swept-wing P-63s that the Navy bought were referred to as L-39s, L being the Navy’s manufacturing letter for the Bell Aircraft Corporation. In the case of the D-558, the D stood for Douglas and 558 was the Douglas model number for the design originally proposed for the Navy’s high-speed research aircraft program. The –1 and –2 differentiated the two types that resulted from the first two phases of the program.

Manufacturers use model numbers for their own internal records, typically assigning each of their designs a number, not always sequential but sometimes actually begun with “1” denoting their first. Not all of these designs are built, of course, and some companies keep two different lists, one for predesign studies and another of projects that have been committed to detail design and fabrication. For marketing reasons, model numbers of committed projects are often not sequential but are based on some hoped for association, the Bell Helicopter Model 209, 309 and 409 gun ships, for example. In some cases what appears to be a Model number, e.g. Boeing 707, is not actually the model number, which was “367-80”, explaining why the prototype was referred to as the “Dash 80”. Design study numbers tend to be sequential since they are assigned by engineering as the need to document a project for future reference arises.
Although there was a third phase in the original 1945 Navy contract with Douglas that resulted in the D-558s, it was for a full-scale mockup of an operational jet fighter, not a third research aircraft type. As it turned out, the mockup requirement was cancelled and the aircraft requirements and specifications contained in the first two phases were considerably revised. The D-558-3 designation has persisted, however, if for no other reason than the direct lineage back to the D-558-1 and –2 research aircraft programs of the follow-on work that did not result in a new contract.
The last of the three D-558-2 Skyrockets was completed in 1949. By November 1953, one of them had been flown to the highest altitude and highest speed that the type was to achieve, both records at the time but soon to be bettered during X-1 flights. The only follow-on high-speed rocket aircraft program at the time was the troubled X-2, and while it would eventually exceed 100,000 feet and Mach 3, the USAF, U.S. Navy and NACA were all interested in going much higher and faster.
In 1954, the Office of Naval Research contracted with Douglas for a predesign study of the next generation of rocket-powered research aircraft, to determine what altitudes were attainable (1,000,000 feet was desired) and recommend design and test requirements. The resulting design has been informally referred to as the D-558-3, in recognition of it being the next Douglas high-performance research aircraft, but was in fact designated by Douglas as their Model 671.

It bore a family resemblance to both D-558 types, combining a straight wing and empennage similar to the –1’s with a fuselage like the rocket powered –2’s. Relatively little detail design definition was provided for the aircraft, however, since it wasn’t required for the purpose of the study. Only enough detail was created to communicate the design concept and make approximate weight, performance and program cost projections. The report stated that configuration changes would likely result as the design evolved.

Among other things, Douglas concluded that while climbing to 1,000,000 feet was doable, pulling out of the subsequent dive was not, the profile closely resembling that of a lawn dart thrown almost vertically. They projected a maximum altitude of 700,000 feet was achievable and on a different flight profile, a maximum speed on the order of Mach 7, assuming success with evaluation of temperature-resistant materials. Other conclusions closely described the actual X-15 program activity.

The USAF and NACA were also considering manned, rocket-powered, hypersonic aircraft projects, the former a Super X-2 and the latter, what eventually became the X-15. Of the three projects, the USAF was the most modest in performance goals and the Navy, the most ambitious but focused on altitude with speed as a literal fallout. The NACA project was intent on achieving Mach 7.

In December 1954, the NACA, Air Force, and Navy agreed to undertake joint development of the proposed hypersonic research aircraft. The performance goals were 250,000 feet in altitude and 6,600 feet per second, roughly Mach 6.7. In January 1955 it received the designation X-15. That same month, the Air Force (which administered the design and construction phases of the project) held the first briefings for potential contractors. This culminated in a competition involving Bell, Douglas, North American, and Republic, their proposals being submitted on 9 May 1955.

Although the design requirements had not changed significantly from the ONR study and the same engine was used, the Douglas proposal only superficially resembled the Model 671 and was given a different Model Number, 684. It was somewhat bigger in every dimension, with the horizontal tail relocated and a ventral fin added, and much greater detail was provided than for the Model 671. The engine remained the same.

The Navy’s George Spangenberg was very impressed by the Douglas proposal for the X-15 program, particularly the innovative way that they met the airframe heating problem with a light weight structure, using magnesium instead of the expected steel. The Model 684 was either a close second, tied for first, or first, depending on how the evaluation data was added up and which agency was polled. However, North American used the preferred basic structural approach, a steel derivative, and was announced the winner on September 30, 1955.

Neither the 1954 Douglas study that described the Model 671 nor the 1955 Douglas proposal of the Model 684 for the X-15 program mention “D-558-3” although they both refer to the D-558-1 and –2. In the unlikely event that the Navy had proceeded with an independent high-performance rocket plane program with Douglas in 1955, it is possible that it would have been designated the D-558-3 in recognition of its heritage, rather than whatever Model number the design might have had at Douglas. In fact, it is likely that the D-558-2, and maybe even the D-558-1, had a different Douglas model number than 558.

Of course if the Douglas proposal of the Model 684 had been selected in the 1955 competition, it would have been called the X-15, not the D-558-3, since that designation has already been identified for the winning design.

Douglas management did have hopes for a hypersonic successor to the D-558s and their lead engineer called it the D-558-3, at least after the fact. In his 1980 book, Combat Aircraft Designer, written with Rosario Rausa, Ed Heinemann includes a chapter on the D-558s and describes the 1953 effort to sell a new research aircraft to the Navy and the resulting 1954 ONR study in some detail, mostly referring to the aircraft as the D-558-3 but also identifying it as the Model 671. He not only doesn’t mention its successor on the Douglas drawing boards, the Model 684, he implies that Douglas did not compete for the X-15 program. The name “Skyflash” is also notable for its complete absence, even in the summary table that lists the D-558-1 and –2 and their popular names along with the D-558-3 but with no name.

In keeping with the lack of rigor in using the D-558-3 designation, an artist’s concept of the Model 684, not the Model 671 that Mr. Heinemann discusses, is used to illustrate the D-558-3 in his book.

Tommy H. Thomason
27 August 2005 Draft
 

Attachments

  • ModelD-671jenkins.jpg
    ModelD-671jenkins.jpg
    108.7 KB · Views: 616
  • ModelD-684Jenkins.jpg
    ModelD-684Jenkins.jpg
    129.1 KB · Views: 1,989

XP67_Moonbat

ACCESS: Top Secret
Joined
Jan 16, 2008
Messages
2,162
Reaction score
56
Archi,

Good job on the artwork as always. I commend you. Ah where does he find those wonderful planes ????
 

archipeppe

ACCESS: Top Secret
Joined
Oct 18, 2007
Messages
1,712
Reaction score
362
XP67_Moonbat said:
Archi,

Good job on the artwork as always. I commend you. Ah where does he find those wonderful planes ????

Many thanks Moonbat, I'm glad to know that you're appreciated my work.... :)
 

overscan (PaulMM)

Administrator
Staff member
Joined
Dec 27, 2005
Messages
12,593
Reaction score
3,907

Nice article, interesting blog.

“D-558-3” is commonly used to identify the proposed Douglas hypersonic research aircraft follow-on to their successful D-558-1 Skystreak and D-558-2 Skyrocket program. Although the designation doesn’t officially exist, that hasn’t hindered its use by aviation historians and others to refer to two somewhat different Douglas designs, the Model 671 and 684. What’s more, the name “Skyflash” is sometimes used in conjunction with the D-558-3 designation but appears to have even less validity.

The original D-558 type name came from the Navy’s practice in the 1940s for identifying aircraft types that they procured for purely experimental reasons and that did not already have a military or civil type identification. In those cases, the Navy simply gave the aircraft a designation that combined the Navy’s letter for the manufacturer with the manufacturer’s internal model number for the design.

For example, the Vought skimmer demonstrator for the F5U program was the V-173 and the swept-wing P-63s that the Navy bought were referred to as L-39s, L being the Navy’s manufacturing letter for the Bell Aircraft Corporation. In the case of the D-558, the D stood for Douglas and 558 was the Douglas model number for the design originally proposed for the Navy’s high-speed research aircraft program. The –1 and –2 differentiated the two types that resulted from the first two phases of the program.

Manufacturers use model numbers for their own internal records, typically assigning each of their designs a number, not always sequential but sometimes actually begun with “1” denoting their first. Not all of these designs are built, of course, and some companies keep two different lists, one for predesign studies and another of projects that have been committed to detail design and fabrication. For marketing reasons, model numbers of committed projects are often not sequential but are based on some hoped for association, the Bell Helicopter Model 209, 309 and 409 gun ships, for example. In some cases what appears to be a Model number, e.g. Boeing 707, is not actually the model number, which was “367-80”, explaining why the prototype was referred to as the “Dash 80”. Design study numbers tend to be sequential since they are assigned by engineering as the need to document a project for future reference arises.

Although there was a third phase in the original 1945 Navy contract with Douglas that resulted in the D-558s, it was for a full-scale mockup of an operational jet fighter, not a third research aircraft type. As it turned out, the mockup requirement was cancelled and the aircraft requirements and specifications contained in the first two phases were considerably revised. The D-558-3 designation has persisted, however, if for no other reason than the direct lineage back to the D-558-1 and –2 research aircraft programs of the follow-on work that did not result in a new contract.

The last of the three D-558-2 Skyrockets was completed in 1949. By November 1953, one of them had been flown to the highest altitude and highest speed that the type was to achieve, both records at the time but soon to be bettered during X-1 flights. The only follow-on high-speed rocket aircraft program at the time was the troubled X-2, and while it would eventually exceed 100,000 feet and Mach 3, the USAF, U.S. Navy and NACA were all interested in going much higher and faster.

In 1954, the Office of Naval Research contracted with Douglas for a predesign study of the next generation of rocket-powered research aircraft, to determine what altitudes were attainable (1,000,000 feet was desired) and recommend design and test requirements. The resulting design has been informally referred to as the D-558-3, in recognition of it being the next Douglas high-performance research aircraft, but was in fact designated by Douglas as their Model 671.

Model D-671 jenkins.jpg

It bore a family resemblance to both D-558 types, combining a straight wing and empennage similar to the –1’s with a fuselage like the rocket powered –2’s. Relatively little detail design definition was provided for the aircraft, however, since it wasn’t required for the purpose of the study. Only enough detail was created to communicate the design concept and make approximate weight, performance and program cost projections. The report stated that configuration changes would likely result as the design evolved.

Among other things, Douglas concluded that while climbing to 1,000,000 feet was doable, pulling out of the subsequent dive was not, the profile closely resembling that of a lawn dart thrown almost vertically. They projected a maximum altitude of 700,000 feet was achievable and on a different flight profile, a maximum speed on the order of Mach 7, assuming success with evaluation of temperature-resistant materials. Other conclusions closely described the actual X-15 program activity.

The USAF and NACA were also considering manned, rocket-powered, hypersonic aircraft projects, the former a Super X-2 and the latter, what eventually became the X-15. Of the three projects, the USAF was the most modest in performance goals and the Navy, the most ambitious but focused on altitude with speed as a literal fallout. The NACA project was intent on achieving Mach 7.

In December 1954, the NACA, Air Force, and Navy agreed to undertake joint development of the proposed hypersonic research aircraft. The performance goals were 250,000 feet in altitude and 6,600 feet per second, roughly Mach 6.7. In January 1955 it received the designation X-15. That same month, the Air Force (which administered the design and construction phases of the project) held the first briefings for potential contractors. This culminated in a competition involving Bell, Douglas, North American, and Republic, their proposals being submitted on 9 May 1955.

Although the design requirements had not changed significantly from the ONR study and the same engine was used, the Douglas proposal only superficially resembled the Model 671 and was given a different Model Number, 684. It was somewhat bigger in every dimension, with the horizontal tail relocated and a ventral fin added, and much greater detail was provided than for the Model 671. The engine remained the same.

D558_III_b.jpg

The Navy’s George Spangenberg was very impressed by the Douglas proposal for the X-15 program, particularly the innovative way that they met the airframe heating problem with a light weight structure, using magnesium instead of the expected steel. The Model 684 was either a close second, tied for first, or first, depending on how the evaluation data was added up and which agency was polled. However, North American used the preferred basic structural approach, a steel derivative, and was announced the winner on September 30, 1955.

Model D-684 Jenkins.jpg

Neither the 1954 Douglas study that described the Model 671 nor the 1955 Douglas proposal of the Model 684 for the X-15 program mention “D-558-3” although they both refer to the D-558-1 and –2. In the unlikely event that the Navy had proceeded with an independent high-performance rocket plane program with Douglas in 1955, it is possible that it would have been designated the D-558-3 in recognition of its heritage, rather than whatever Model number the design might have had at Douglas. In fact, it is likely that the D-558-2, and maybe even the D-558-1, had a different Douglas model number than 558.

Of course if the Douglas proposal of the Model 684 had been selected in the 1955 competition, it would have been called the X-15, not the D-558-3, since that designation has already been identified for the winning design.

Douglas management did have hopes for a hypersonic successor to the D-558s and their lead engineer called it the D-558-3, at least after the fact. In his 1980 book, Combat Aircraft Designer, written with Rosario Rausa, Ed Heinemann includes a chapter on the D-558s and describes the 1953 effort to sell a new research aircraft to the Navy and the resulting 1954 ONR study in some detail, mostly referring to the aircraft as the D-558-3 but also identifying it as the Model 671. He not only doesn’t mention its successor on the Douglas drawing boards, the Model 684, he implies that Douglas did not compete for the X-15 program. The name “Skyflash” is also notable for its complete absence, even in the summary table that lists the D-558-1 and –2 and their popular names along with the D-558-3 but with no name.
 
Last edited:

archipeppe

ACCESS: Top Secret
Joined
Oct 18, 2007
Messages
1,712
Reaction score
362
Such a satisfaction!!

The three-view drawing enclosed to the article is a mine one......

Thanks Admin!!! :D
 

lark

ACCESS: Top Secret
Senior Member
Joined
Feb 17, 2006
Messages
1,806
Reaction score
77
I was much surprised to read in the article about a planned
fighter variant mock-up in the third phase...
 

fightingirish

ACCESS: Top Secret
Senior Member
Joined
Jun 3, 2006
Messages
2,397
Reaction score
734
A picture showing the Douglas D-558-1 Skystreak. In colour!!! :eek: B) :)


Link: http://www.corbisimages.com/stock-photo/rights-managed/U000391ACME/us-navy-officers-inspecting-douglas-skystreak-jet
 

hesham

ACCESS: USAP
Senior Member
Joined
May 26, 2006
Messages
27,092
Reaction score
3,768
From Air Pictorial 12/1956,


here is a strange notify about Douglas 4 to 5 Mach aircraft under study and could
bear a high temperature degrees,I can ID it,please don't tell me it was a Douglas
Skyflash,the Skyflash abandoned completely in 1955,and we are here in 12/1956 ?.
 

Attachments

  • Douglas.png
    Douglas.png
    206.8 KB · Views: 73

Stargazer2006

ACCESS: USAP
Senior Member
Joined
Jun 25, 2009
Messages
13,227
Reaction score
471
If I'm not mistaken, "Skyflash" was never an official company name to begin with. It was coined by a model maker to render their model more attractive...
 

hesham

ACCESS: USAP
Senior Member
Joined
May 26, 2006
Messages
27,092
Reaction score
3,768
My dear Skyblazer,


I meant,the Douglas Model-684 was abandoned in 1955,so this aircraft in Air Pictorial
magazine was anther one.
 

Steve Pace

Aviation History Writer
Joined
Jan 6, 2013
Messages
2,268
Reaction score
40
archipeppe said:
Maveric said:
I believe the D.558-III "Skyflash" is the Douglas D.684?

Yes it is.
It was conceived as concurrent for the X 15 original proposal, won (at least) by NAA ESO 7487.

I enclose my personal contribution in matter.
Great artwork, Giuseppe! -SP
 

Dynoman

ACCESS: Top Secret
Senior Member
Joined
Jul 29, 2009
Messages
912
Reaction score
276
Skyflash from NASA.
 

Attachments

  • Skyflash.jpg
    Skyflash.jpg
    308.5 KB · Views: 116

Dynoman

ACCESS: Top Secret
Senior Member
Joined
Jul 29, 2009
Messages
912
Reaction score
276
Douglas D-671 inboard layout and D-671 flight trajectory.
 

Attachments

  • D671.jpg
    D671.jpg
    200.8 KB · Views: 104
  • D671_Flight.jpg
    D671_Flight.jpg
    270.3 KB · Views: 101

RAP

ACCESS: Top Secret
Top Contributor
Senior Member
Joined
Jan 29, 2008
Messages
687
Reaction score
399
Some nice drawings of the 684. Note on the inboard drawing the possible observer arrangement.
 

Attachments

  • 684 profile and data.jpg
    684 profile and data.jpg
    341.9 KB · Views: 131
  • Model 684 inboard.jpg
    Model 684 inboard.jpg
    821 KB · Views: 148
  • 684 top & head on.jpg
    684 top & head on.jpg
    123.4 KB · Views: 132
  • 684 sectionals.jpg
    684 sectionals.jpg
    269.3 KB · Views: 128

Similar threads

Top