P-40Q vs P-60A/D

[Shortround6]

To go one at a time:

The P-40Q had the fuselage cutdown for the bubble canopy (eventually) which I'm sure was a significant engineering task

I don't know. A number of other aircraft were certainly cut down and fitted with bubbles. While there is a change in tooling and fixtures each plane may be an individual when it comes to how this relates to strength/structure and airflow to the rudder. It may be a simple task or not.

The Q also had to have more engineering work done to integrate the new "nose" / coolers / radiators into the K/N front section

I believe (and could be wrong) that this is where the majority of the work was done. It is essentially forward of the "fire wall" although it is possible the fire wall was moved. On 90 something percent of the fighters built in WW I the cowling and exterior of the fuselage/engine covering had NO real structural function aside from holding itself together.

The standard P-40 wing had to be "clipped", plus tooled for more cooling ducts and possibly two more guns (total of 6)/ or cannons

Clipping may require very little work as the wing tips outboard of the ailerons were a separate structure bolted/fastened to the last real wing rib at that point. Much like the Spitfire or Zero wing tips. Leave off the original wing tip and build fit new shorter one down to a fairing strip or cover.

The "story" ( and could be wrong) is that the P-40Q used the inner gun bay (Or space for inner gun) for space for cooler with the new intake and exhaust. In fact this "story" may be in error.

Spacing seems to too far from the other guns unless the air took a detour outwards from the scoop (possible if the area required for the cooler exceeded the height available in the new duct.) but it also appears that the intake was not into the wing itself but a duct scabbed onto the bottom of the wing or a combination. Could be wrong but most photos aren't much better. This may well leave room for the restoration of the 6 gun armament with little trouble.

The P-60A wing had inward swinging gear (engineering work already done for the Warhawk fuselage integration)

The only real "integration" is running control/hydraulic and electric lines. P-40 wing and fuselage were such that the fuselage sat on top of the wing. the wing was not attached to each side of the fuselage.

Now where Curtiss put the fuel on the P-60 I don't know and what the arrangement of spars were on the P-60 I don't know. Given the extra 40 sq ft of wing area and the need to move the guns outwards to clear a bigger propeller there may have been more room in the P-60 wing to put things. Or the deeper fuselage may have allowed for the fuel tank to be above the landing gear?

If all you are planning to keep on the P-53/60 is the basic fuselage from firewall to rudder post and above the wing you have a lot more scope to move things around than trying to keep the existing wing structure like the P-40Q.

 

[Shortround6]

A few more pictures of the XP-40Q

and a model

The duct on the model doesn't seem to quite match the drawing or the location quite match the photos but since there were two/three different bubble top "Q"s you can't be sure something is wrong unless you have the serial numbers and/or date.

We KNOW the first "Q" started without the bubble and had a different engine.

It looks like the duct IF it got larger near it's middle as the drawing and at least one photo show, could have intruded on the gun space. Since the gun access panel is on the bottom of the wing (ammo went in the top) getting pictures of the gun bays is going to be hard.

 

[BiffF15]

Shortround,

The last shot is very tellling, as it looks like the first mod was to cut down the fuselage and add the bubble canopy. The nose of that particular airplane looks to be unmoded and sporting a 3 blade prop.

If the plane did have radiators or ducting occupying space the an inboard gun would normally go in, it would be "lightly armed" to say the least. I thought if they went to a more normal inward retracting gear then it would open space for radiators and weapons (move the rad's more inboard from where they currently are depicted. Of course, looking at things in 2014 is a bit different than the early 40's.

Cheers,
Biff

 

[GregP]

Hi Biff,

I don't know for sure, but if you look at the picture of the model it looks as if the vertical space between the bottom of the exhaust manifolds and the bottom of the cowling appears to be about the same height as the spinner.

If you thn look at the last pic, it looks as if the vertical space between the bottom of the exhaust manifols and the bottom of the cowling has a similar comparative measurement.

It's tough to really tell for sure, but the cowling could be after modification.

Can't argue the 3-bladed prop, though.

 

[Shortround6]

One book says that the wheels were 8ft 2 1/2in from center of tire to center of tire. The tires were also 30in in diameter.

The Mustang was 11ft 10in.

You need landing gear long enough to keep the prop out of the dirt

I won't say it was impossible, the P-47s landing gear got shorter as it retracted (about 9 in ?) and the F8F used a double hinge;

But it does add another layer of complication.

 

[GregP]

Watching a Bearcat gear retraction on jacks is very interesting.

Most people have never noticed that the gear is double hinged and are very surprised when they see it in person. They can look right at it and never realise how different it is because they are not paying attention to the details, they are just looking at airplanes. Some of these people are pilots, many are A&P mechanics. Once you point it out, the mechanics usually want 50 pictures of it up close, just because it is so unusual.

 

[BiffF15]

GregP,

Also note the "carb intake"? on top of the nose (like the standard P-40) which is not present on any other P-40Q shot I remember seeing. It seems that the particular shot we are looking at is just after the canopy change. Leads one to wonder why they didn't do it to the standard P-40 since it looks to be a drastic improvement in visibilty.

Cheers,
Biff

 

[GregP]

Hi Biff,

Methinks you are correct. Since the carb air scoop is there, it's probably as you said earlier. I was trying to figure the cowl height and ignored the scoop in front of my eyes.

 

[m37b1]

That's an XP-40N. Standard P-40 with experimental bubble canopy. This was also included on the Q.

 

[Shortround6]

The Curtiss fighter timeline is long and convoluted and some of what is printed doesn't make sense (at least to me) so I will try to set out a chronology. Just of orders/first flights/ first production of major models. NO PERFORANCE.
Each series has it's own color, and I left out the XP-42

Nov 1934-construction of prototype Hawk 75 begins.
May 1935 first flight of Hawk 75 with Curtiss XR-1670 engine.
June 16, 1936 Curtiss gets an order for 3 Y1P-36 aircraft.
Feb 16 1937 Army orders XP-37
March of 1937 sees delivery of first Y1P-36 and testing is done at Wright Field in June.
April 1937 sees XP-37 fly the first time.
July 7, 1937, the Army ordered 210 P-36As
July 1937 Don Berlin gets permission to install a V-1710-19 in the 10th P-36 airframe to create the XP-40
December 11, 1937 Army orders 13 YP-37s.
April of 1938 sees first production P-36 delivered.
October 14, 1938 sees XP-40 fly the first time.
April 26, 1939 sees contract of 524 P-40s placed.
June 1939 sees first YP-37 delivered.
September 29, 1939 sees Army order two XP-46 Prototypes.
November 27, 1939 has USAAC issue Circular Proposal R-40C which leads to the XP-55
April 4, 1940 Sees first production P-40 delivered.
May 1940 sees the British (and French) order the model 87 which would become the P-40D/E
June 10, 1940 Sees the proposed substitution of the modified P-40 (D/E)for the experimental P-46
June 22, 1940 sees the USAAC issue a contract for preliminary engineering data and a powered wind tunnel model for the XP-55.
October 1, 1940, the USAAC ordered two examples of the Model 88 under the designation XP-53
Nov 15th (?)1940 sees the start of the P-60 project with one of the P-53 airframes to be powered by a Packard Merlin V-1650-1
February 15, 1941 sees the XP-46A (unarmed) fly
April 29, 1941 sees Curtiss submit proposal for the XP-62 to an Army requirement issued in Jan
June 27, 1941 sees Army place a contract for two XP-62 prototypes, one to finished in 15 months and one in 18 months. .
June 30, 1941 sees the first flight of a P-40F prototype with a Merlin 28 engine
July 1941 1941 sees first deliveries of the Kittyhawk I/P-40D/E
September 18, 1941 sees first flight of Melrin powered XP-60
September 29, 1941 first flight of XP-46 (armed)
October 21, 1941, a contract for 1950 P-60As is placed using turbo-charged Allison engines.
October 28, 1941, 600 P-40Ks were ordered for Lend-Lease supply to China. It was envisaged that this would be the last P-40 model to be built in quantity, the P-60 replacing the P-40 on the Curtiss production lines thereafter
November 1941 sees the P-53 airframe assigned to the P-60 project.
December 2, 1941 sees the low powered flying test bed for XP-55 program first flight.
December 20, 1941, work on the P-60A project was ordered halted, but it was decided to continue with 3 prototypes, two with Allison engines, one with a GE turbo and one with a wright turbo. Third airframe was to get the Chysler V-16.
Jan 1942 sees first production P-40Fs with Packard Merlin engines.
May 1942 sees first production P-40Ks come off the line. (some sources say Aug ?)
July 10, 1942, a USAAF contract was issued for three prototypes under the designation XP-55.
August, 1942 sees original XP-60 repowered with two stage Merlin V-1650-3 and renamed XP-60D
November 11, 1942 sees first flight of XP-60A with Allison but without turbo
Nov 1942 also sees Curtiss propose using the P W R-2800 on the P-60 airframe. Army buys it to the tune of a 500 plane order.
Nov 1942 sees first P-40Ms built with Allison engine using 9.60 supercharger gears. None are for US use, all are for lend-lease.
December 2, 1942 sees Army cancel the XP-60 with Allison engine and Wright turbo and substitute P W R-2800 with single rotation prop instead of contra props. designated XP-60E
March 1943 sees first of the Lightweight P-40N-1s
March 1943 also sees at least ground testing of first XP-40Q although it might be with a single stage engine?
May 26, 1943 sees first flight of XP-60E
July 19, 1943 sees first flight of XP-55
July 21, 1943 sees the XP-62 program pretty much canceled after delays and official flip-flops, limited work to continue for research.
Dates for XP-40Q are hard to come by, we know it was being tested (2nd airframe ?) in Nov 1943.
Nov 30 1944 Last P-40N-40 rolls out the door.

I hope this helps.
Hopefully it shows that Curtiss was NOT sitting back fat, dumb and happy building P-40s

 

[Shortround6]

That's an XP-40N. Standard P-40 with experimental bubble canopy. This was also included on the Q.

I believe you are correct. Descriptions of the 1st XP-40Q say it kept the turtle back and kept the top mounted airscoop, at least to start.

 

[m37b1]

Nice job! I'll need to draw a family tree for the Curtiss efforts.

 

[GregP]

It'll look more like a weed.

 

[drgondog]

I believe you are correct. Descriptions of the 1st XP-40Q say it kept the turtle back and kept the top mounted airscoop, at least to start.

The first XP-40Q was P-40K-10 42-9987. I once found an obscure pre-flight test reference report citing engine vibration rests in May 1943 for 9987.

 

[GregP]

I've posted it before in here, but here's my drawing of an XP-40Q. Actually I drew the 3-View. The 3-D illustration came off the web and I added it just for decoration ... it's not my work.

I might have to do one of XP-4Q #1, but the problem would be to find good views all taken at the correct point in time ....

 

[m37b1]

Man! That plane looks good from any angle!

 

[GregP]

Does, doesn't it? Even if it wasn't put into production it sure LOOKS like it should have been.

Ah well, no use crying about what didn't happen and, as I've said before, the alternative planes we DID produce did the job quite well.

 

[vikingBerserker]

Man that is a good looking aircraft!

 

[BiffF15]

Yeah, the Q is definitely my favorite looking P-40 as well!

 

[davparlr]

back to an off subject topic.


I read your review of the XP-56 on another site and I thought it was very good and generally well thought out. However, there are several areas that still cause me mental confusion (not a difficult thing). I'll address these as I go along.

Quickly reading back through the book American Secret Pusher Fighters of World War II by Gerald H Balzer, I've found that the fusealge alone wasn't thought to be the culprit for flow separation and the poor performance of the aircraft.

I agree, it looks pretty smooth

The wing was thick (18%), which would not help,

true, but the F8F also had 18% thickness

but it was the wing/fuselage interface which caused the flow disruption, due to the change in cross sectional area.

definitely could be the problem however other aircraft had reducing cross sectional area interfacing with the wing interface, the F8F and F6F are a couple. These reductions were less than the XP-56 but it in turn was much less than that of the B-36.

The cooling intakes at the leading edge of teh wing were also thought to cause some flow disruption.

also possible. They look clean and not particularly different from other successful designs. Internal ducting could also have caused a problem which could also affect engine performance. They also do not look as near as disruptive as the Do 335 aft engine cooling intake would be.

A bit more on exhaust location. In the thread "B-36 – Why a Pusher" post #23 clearly shows the exhaust exits are located at about 50% of the length of the props and about 6 ft in front of the props. The XP-56 exhaust at approx 10% of the length of the prop and about 4 ft in front of the prop. However, I do not think either one of these is a big issue. Unless the fuselage is in stall, an intolerable situation, the airflow will follow the outline of the fuselage which would keep any turbulence from the exhaust close to the hub, and the least sensitive part, of the prop. This is apparent by the exhaust stains on the sides of airplanes.

NACA's performance summary of the XP-56 estimated its top speed to be 340mph. Clearly there was more than an underperforming engine at play.

I am not sure this was done by NACA but rather by the military. In any case, I think this was just an extrapolation of flight test data and not a technical analysis of the design.

The XP-56 did not meet its performance criteria. It may have been a serious design flaw or a combination of some or all of the above issues, or a faulty engine. A component analysis indicates a solid design. The fuselage appears to be as clean and aerodynamic design as possible. It is bit portly for my liking but portly does not mean aerodynamically inefficient (the Bell X-1 was a bit portly, too). The wings, while a bit thick, was not out of the mainstream of high performance design and was similar to other aircraft in overall size, and it was swept which could have provided a much better limiting mach. Add on to that well know vertical tail designs and that is the overall aerodynamics, nothing stretching technology. The interfaces of all that could indeed be a problem, but again, something not new technology, something wind tunnel testing could identify, and reasonable fixes could be made. My overall feelings, based on pilot reports on heavy nose flying and effort to keep the plane flying, is that the plane was never properly trimmed or Cg properly placed. Both could affect top speed and fuel performance. However even if the fixes were simple and the performance criteria was met, the plane was advanced and would have taken some time to work out the issues of a horizontal tailless flying and also operating a swept wing aircraft. The need for these planes had passed.

Without wind tunnel data, we will never know. And, as with so many old aircraft operations, the endless debate goes on.