Convair B-36 Derivatives (B-36C)

[codeone]

Artist concept just posted on Code One Magazine website. Spotlight photo and also put it in the B-36 gallery.

Enjoy.

The B-36C was a modification to the B-36 design proposed in the mid 1940s. The R-4360 engines would be replaced with four Wright Aeronautical gas turbine engines for propeller drive and four General Electric TG-180 gas turbine engines for jet propulsion. The two engine types were paired and mounted in tandem nacelles. The jet nozzles were directed three degrees downward and three degrees outward to so that the hot gasses did not burn the horizontal tail.

 

[Orionblamblam]

Interestingly, it shows a reversion back to the original Ginormous Huge Single Main Wheel as used on the B-36 proptotype.

 

[GTX]

Interesting, I thought the "B-36C was to be powered by six 4300 hp Pratt & Whitney R-4360-51 variable discharge turbine (VDT, or turbocompound) engines. In the VDT engine, exhaust gases from the piston engine would pass through a General Electric CHM-2 turbosupercharger which featured a clamshell nozzle that could create a jet thrust by varying the size of the turbine exit. The variable discharge nozzle was to be operated by automatic control activated by a manifold pressure sensor. "

Source

regards,

Greg

 

[codeone]

This derivative study dates from very early in the program (1945 I think).

 

[codeone]

I have a cutaway graphic of the engine somewhere. Will post it soon.

 

[codeone]

Posted engine cutaway on our homepage. I'll attach here.

 

[OM]

...You know, this thread's probably the best place to pose this puzzler: in retrospect, was the choice of pusher over tractor in the B-36's design actually the best choice? What -were- the motivating factors in the first place for Convair's decision in this regard?

 

[Stargazer]

...You know, this thread's probably the best place to pose this puzzler: in retrospect, was the choice of pusher over tractor in the B-36's design actually the best choice? What -were- the motivating factors in the first place for Convair's decision in this regard?

You mean "tractor over pusher", right? ;D

 

[JFC Fuller]

A quick google books search came up with this snippet from Aviation Week and Space Technology:

1947-JB-36C program suggested to Air Staff by converting last 34 of 100-plane program to VDT-tractor versions. Increased costs of B-36C program to be met by cutting total program back from 100 to 95 planes. ...

And according to Robert F. Dorr in '7th Bombardment Group/Wing, 1918-1995'

This version was known as the B-36C and would have gone to the 7th had it materialized. But the VDT engines had bigger problems of their own, and the B- 36C was never built.

I always though it was a shame that they abandoned the original B-29 nose glazing, the B-36 looked much more elegant with that.

The design in the first post would have had 4 GE/Allison J35's and I assume that the turboprops would have been the Wright J-37?

 

[Stargazer]

I always though it was a shame that they abandoned the original B-29 nose glazing, the B-36 looked much more elegant with that.

But wasn't the B-60 supposed to fly at higher altitudes and faster than the B-36? Glazed nose might have been awkward and even dangerous in those conditions.

 

[Bill Garvin]

...You know, this thread's probably the best place to pose this puzzler: in retrospect, was the choice of pusher over tractor in the B-36's design actually the best choice? What -were- the motivating factors in the first place for Convair's decision in this regard?

The motivating factor was to reduce drag and thus push range up as much as possible. In retrospect, probably not the best solution but given the extent of knowledge at the time, it was an easy mistake to make.

I always though it was a shame that they abandoned the original B-29 nose glazing, the B-36 looked much more elegant with that.

Cost of mounting a twin 20mm turret in the nose. Also, the all-glazed nose on the B-29 caused a lot of problems with instrument layout and reflections off the transparencies.

 

[OM]

...You know, this thread's probably the best place to pose this puzzler: in retrospect, was the choice of pusher over tractor in the B-36's design actually the best choice? What -were- the motivating factors in the first place for Convair's decision in this regard?

You mean "tractor over pusher", right? ;D

...Nope. The way I learned it, if the prop's behind the wing, it's a pusher. Which is how the B-36's butter paddles were mounted.

 

[Orionblamblam]

What -were- the motivating factors in the first place for Convair's decision in this regard?

IIRC, it was so that the propwash wouldn't go over the wing surface and mess up the clean aerodynamics. The B-36 was, after all, designed to be pretty clean... it had to be, since it was meant to fly from the US to Festung Europa and back without refueling.

 

[frank]

A similar situation. I've not flown one personally, but I've heard from several who have, the push-pull Cessna Skymaster flies better on the rear / pusher engine alone rather than the front / tractor engine alone, due to better aerodynamics from being 'pushed'.

What -were- the motivating factors in the first place for Convair's decision in this regard?

IIRC, it was so that the propwash wouldn't go over the wing surface and mess up the clean aerodynamics. The B-36 was, after all, designed to be pretty clean... it had to be, since it was meant to fly from the US to Festung Europa and back without refueling.

 

[JFC Fuller]

Interestingly the model shows 3-bladed propellers whereas the wooden mock-up appears to have a propeller hub with stubs for blades implying a 4 bladed propeller configuration.

So some random googling reveals to me (known to most others I am sure) that the Boeing YB-50C and the B-54A production aircraft were to have used the R-4360-51VDT, the existing B-54 threads are here:

http://www.secretprojects.co.uk/forum/index.php/topic,5826.0.html

and

http://www.secretprojects.co.uk/forum/index.php/topic,10693.0.html

It was estimated that an R-4360-51 VDT engined B-36C would have a service ceiling of 45,000ft and a maximum speed of 410mph. The main problems with the VDT engine were the cooling and the control of the discharge nozzle itself.

B-36C productions was allocated serials 44-92065 through 44- 92098.

 

[Howedar]

Four blades (or two, or six) would be unfavorable from a vibration perspective, as you'd have a pretty strong mode associated with two blades passing through the wing wake at the same time. Three blades does not have this problem. Neither does five etc, but less blades tends to be more efficient, as long as you're not running into sonic tip or ground clearance issues.

 

[blackkite]

What is this?

http://modernwartech.blog.hu/2016/11/22/a_b-36_vetelytarsai_tovabbfejlesztese_es_az_nb-36h_az_ismerteto_6_resze

 

[blackkite]

Oh B-60 variant!! Thanks a lot.

 

[circle-5]

Another view of this model, currently on display at Fort Worth.

 

[blackkite]

Thanks!! Excellent information.
Wright T35 engine.
T35 description.
https://airandspace.si.edu/collection-objects/wright-typhoon-xt35-w-1-turboprop-engine
"Type: Turboprop
Power Rating: 4,451 kW (6,090 eshp) at 7,080 rpm
Compressor: 3-stage centrifugal
Combustor: Annular
Turbine: 3-stage axial
Weight: 2,699 kg (5,950 lb)"

YB-60 with T35 three side view.
http://beyondthesprues.com/Forum/index.php?topic=418.30
XB-52 with T35 three side view.
http://aerothusiast.com/usaf-turboprop-testbeds-yc-97j-yc-121f-yc-124b/

Bottom drawing shows Boeing XB-52 (1948) – The B-52 was originally to be powered by Wright T35 turboprops.

Russian T35 site.
http://military-informant.com/c111-history/letayushhaya-laboratoriya-ev-17g-na-ispyitaniyah-turbovintovogo-dvigatelya-xt-35-typhoon.html

I found two sectional drawing for T35. Two stage compressor type and three stage compressor type.

 

[famvburg]

All of the drawings and pics show a 4 engined version, not twin.

 

[blackkite]

Hi! Larger image. ;D

http://beyondthesprues.com/Forum/index.php?topic=418.15

 

[PlanesPictures]

_

 

[blackkite]

Wow!! What is this unmanned vehicle?

 

[starviking]

Wow!! What is this unmanned vehicle?

Northrop Boojum supersonic cruise missile.

Ref: https://en.wikipedia.org/wiki/SSM-A-5_Boojum

 

[blackkite]

Thanks a lot,Gentlemen.

 

[LowObservable]

Presumably, the Boojum's warhead ensured that the target would softly and suddenly vanish away.

 

[blackkite]

Hi!

http://ghostmodeler.blogspot.jp/2014_01_01_archive.html

 

[Grey Havoc]

Presumably, the Boojum's warhead ensured that the target would softly and suddenly vanish away.

;D

 

[ZacYates]

As cool as the swept-wing concepts are, this initial one really took my fancy:

Artist concept just posted on Code One Magazine website. Spotlight photo and also put it in the B-36 gallery.

Enjoy.

The B-36C was a modification to the B-36 design proposed in the mid 1940s. The R-4360 engines would be replaced with four Wright Aeronautical gas turbine engines for propeller drive and four General Electric TG-180 gas turbine engines for jet propulsion. The two engine types were paired and mounted in tandem nacelles. The jet nozzles were directed three degrees downward and three degrees outward to so that the hot gasses did not burn the horizontal tail.

Are there any other drawings/models of this one out there?

 

[blackkite]

As cool as the swept-wing concepts are, this initial one really took my fancy:

Artist concept just posted on Code One Magazine website. Spotlight photo and also put it in the B-36 gallery.

Enjoy.

The B-36C was a modification to the B-36 design proposed in the mid 1940s. The R-4360 engines would be replaced with four Wright Aeronautical gas turbine engines for propeller drive and four General Electric TG-180 gas turbine engines for jet propulsion. The two engine types were paired and mounted in tandem nacelles. The jet nozzles were directed three degrees downward and three degrees outward to so that the hot gasses did not burn the horizontal tail.

Are there any other drawings/models of this one out there?

I will try this. Perhaps it takes long time.

 

[blackkite]

Hi! Another one. Powered by eight T-35 engines?(Or eight R-7755 engine with skin cooler?)

http://beyondthesprues.com/Forum/index.php?topic=418.0;all

"Not as "high-tech" perhaps as eight XT35's, but eight XR7755's would have had the same horsepower and likely could've used the same propellers. The radiators would've required some nacelle design changes, but nothing major compared to what's already shown here."

http://www.ebay.com/itm/PLS-144002-1-144-B-36-Peacemaker-strategic-bomber-Full-Size-Scale-2xA1-Plans-/272559700700

Deatail drawing with Russian language is here.
http://www.airwar.ru/other/draw2/b36aiv.html

 

[RAP]

Some info from 1950 Convair report.

 

[hesham]

Nice find RAP.

 

[GTX]

Very cool.

 

[RyanC]

NARA II, College Park, MD
RG 342
Entry P-26
Box 3685

Folder: 452.1
Consolidated B-36
Confid 1945-46-47-48

Declassified via NND 917647

----------------------

IN REPLY ADDRESS BOTH COMMUNICATION AND
ENVELOPE TO COMMANDING GENERAL, AIR MATERIEL
COMMAND, ATTENTION FOLLOWING OFFICE SYMBOL:
MCPPXA3/TPG:ICW/3-1334

HEADQUARTERS
AIR MATERIEL COMMAND
WRIGHT-PATTERSON AIR FORCE BASE
DAYTON, OHIO

(Undated)
(Filed Date)
25 [illegible] 1948)

SUBJECT: B-36 Program.

TO: Chief of Staff,
United States Air Force,
Washington 25, D. C.

Attention: Deputy Chief of Staff, Materiel.

1. Reference is made to Hqs. USAF directive dated 5 December 1947 which approved the B-36 VDT production program. The Air Materiel Command has reexamined this program because increased engine cooling requirements preclude meeting the original estimated performance. The B-36 engine installation is critically affected by increased cooling requirements due to location of the engines in the rear portion of the wing and the high altitude at which the airplane is designed to operate.

2. The basic causes of airplane performance loss are:

a. Additional horsepower required to drive higher capacity cooling fan with resultant loss of 49 MPH cruising speed.
b. Additional airplane weight empty increases caused by the latest power plant installation requirements.
c. Increased drag estimates based on wind tunnel tests amounting to 9 MPH cruising speed penalty.

3. In accordance with the Contractors latest performance estimates, which are concurred in by the Air Materiel Command, the VDT airplane has a maximum range of 7,250 nautical miles at an average cruising speed of 228 knots. The B-36B Airplane has a cruise speed of 248 knots for the same range, and its maximum range is 8,620 nautical miles at 180 knots. Therefore, the Air Materiel Command recommends cancellation of the VDT program. (Comparative performance curves are contained in Attachment "A").

4. In view of the foregoing, it appears advisable to again evaluate the B-36 program based on operational requirements. One of the four following courses of action can be taken:

a. Revert to the original B-36 program; 22 B-36A and 78 B-36B Airplanes, This program can be completed by February 1950. At the present time, it appears that the 100 B-36A and B-36B Airplanes can be completed within funds available on the airframe contract. An additional cost of approximately $1,500,000 will be required to reinstate Government Furnished Property procurements and cover costs incurred to date on B-36 VDT GFP development and production.

b. Terminate at 61 airplanes, thereby cancelling the airplanes scheduled for VDT engine installation. If termination of a quantity of B-36 Airplanes is contemplated, the 61st airplane is the most economical point at which to terminate, since a large amount of the airframe and GFP components has already been stopped at 61st airplane pending release of engineering information for the VDT program. Termination at this point will allow recovery of approximately $92,000,000.

c. Terminate all but 41 B-36 aircraft. This program would obtain for the Air Force the 18 B-36B Airplanes which are currently included in the "GEM" program, one test B-36B, and 22 B-36A Airplanes. (A tentative requirement has been established by Hqs. USAF for modification of 12 B-36A aircraft as tankers to refuel the B-36B aircraft included in the "GEM" program.) Termination at this point will allow recovery of approximately $133,000,000.

d. Terminate the B-36 program delivering only the 22 airplanes which are essentially shop completed. One of these airplanes has already been delivered for static test. The additional 21 airplanes require incorporation of late change requirements and flight test prior to delivery. Termination at this point will allow recovery of approximately $167,000,000.

Note: A breakdown of estimated costs and funds recoverable in support of the above alternate plans is set forth in Attachment "B".

5. Early decision of Headquarters, USAF is required in order that a revised program may be instituted at a minimum cost.

/S/
JOSEPH T. MCNARNEY,
GENERAL, USAF,
COMMANDING.

Incl. Attachments "A" and "B".

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Attach A attached as VDT.gif

B not done so far.

------------

Basic Com. fr Hq AMC, Wright-Patterson AFB, Dayton, Ohio, undated, subject: B-36 Program.

1st Ind.

HQ UNITED STATES AIR FORCE, Washington 25, D. C. 25 June 1948

TO: Commanding General, Air Materiel Command, Wright-Patterson AFB, Dayton, Ohio

1. It is directed that such action be taken on this program as was decided upon at the conference in the Office of the Secretary of the Air Force on 24 June 1948. General Wolfe represented your Command at this conference.

BY COMMAND OF THE CHIEF OF STAFF:

/S/
H.A. CRAIG
Lt. General, U.S.A.F.
Deputy Chief of Staff, Materiel

2 Incls.
n/c

7-13-48 - The decision made by higher authority in the conference referenced above, is to the effect that the 34 B-36 type airplanes, comprising one YB-36C and 33 B-36C airplanes, be cancelled, and that in lieu thereof there be procured 34 additional B-36B airplanes. This will make the program for B-36 airplanes, which is covered by contract W33-038 AC-7 read as follows:

22 B-36A airplanes
73 B-36B airplanes
95 Total

The previous cancellation of 5 airplanes from this program under authority of TI-2036, Addendum #10, which action was taken at the time it was contemplated procuring 34 B-36 series airplanes, will remain the same.

/S/
K.B. WOLFE
Major General USAF
Director, Procurement and Industrial Planning

 

[GTX]

 

[Basil]

Hi! Larger image. ;D

 

[Basil]

Blackkite, thx for posting; very interesting propulsion unit with single rotation staggered transsonic propellers. Similar concepts are investigated again nowadays.

 

[Basil]

... a supersonic staggered single rotation 6 blade prop can be seen on the two photos under the the section "The Third XF-84H" in this document:

XF-84H Propulsion