Early Mustangs-performance/experience?
- Thread starter IdahoRenegade
- Start date
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Data Sheet info (service ceilings at max/mean weights):
Beaufighter I (Herc III)
28,900 max
30,000 mean
Beaufighter II (Merlin XX)
30,800 max
32,600 mean
Defiant I (Merlin III)
28,400 max
31,000 mean
Defiant II (Merlin XX)
32,900 max
34,000 mean
Hurricane I (Merlin III)
32,500 max
33,500 mean
Hurricane IIa (Merlin XX)
37,000 max
37,500 mean
Beaufighter I (Herc III)
28,900 max
30,000 mean
Beaufighter II (Merlin XX)
30,800 max
32,600 mean
Defiant I (Merlin III)
28,400 max
31,000 mean
Defiant II (Merlin XX)
32,900 max
34,000 mean
Hurricane I (Merlin III)
32,500 max
33,500 mean
Hurricane IIa (Merlin XX)
37,000 max
37,500 mean
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What is the serial number of that Mosquito? Your data does not agree with British government testing.
For starters, I found only one Mosquito with Merlin 20 series engines that actually completed climbing trials at the A&AEE. And the report was dated from September 1943.
At the lightest load recorded, Mosquito FB VI - HJ679 had a service ceiling of only 29,800 feet (take-off weight 21,020 lbs). With weight increased to 21,985 lbs. the service ceiling fell to 29,100 feet. Merlin 25 engines.
A&AEE climbing trials were terminated for Mosquito II - W4052, because the Merlin 21 engines kept cutting out above 24,000 feet.
Other planes tested by the A&AEE included:
Mosquito II - W4076 (Merlin 21). Speed checks up to 25,000 feet. No climbing trials.
Mosquito II - W4096 (Merlin 21). Speed checks up to 24,000 feet. No climbing trials.
Mosquito IV - DK290 (Merlin 21). Speed checks up to 24,000 feet. No climbing trials.
Mosquito VI - HX809 (Merlin 25). Speed checks up to 18,000 feet. No climbing trials.
Mosquito XX - KB328 (Merlin 31). Speed checks up to 28,000 feet. No climbing trials.
This was a Canadian-built Mosquito IV with Packard version of Merlin 21s.
Not according to pilots who returned from those missions.
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Shortround6
Major General
I believe, but could very well be wrong, that there was a difference between the crankcases of the two engines. The area at the back of the crankcase being different to accommodate the two speed drive for the supercharger?
This means, if I am correct, that a production line tooled up for production of Merlin X engines could be switched over to Merlin XX's pretty easily while a line making Merlin IIIs or XIIs could not. But they could make Merlin 45s with less trouble.
There seems to be an intermediate section between the crankcase proper and the supercharger which is where a number of "accessories" are located, like magnetos, starter motors,, generators and some odd pumps (hydraulic, vacuum etc) perhaps it is the tooling for this section which is different?
This may also be the difference between Packard engines and British engines as Packard used a different supercharger drive/shift mechanism.
The Merlin XX and 45 used the same supercharger (at least internal and front cover/inlet)
The main point, which we are loosing sight of, is that the Merlin XX made 1175hp at 20,500ft compared to the 840-850hp (?) the early Allison made at the same/similar altitude, which would obviously affect the performance at 20,000ft and above.
The Merlin 61 was rated at 1390hp at 23,500ft which really explains the difference between an Allison Mustang and a Merlin Mustang.
This means, if I am correct, that a production line tooled up for production of Merlin X engines could be switched over to Merlin XX's pretty easily while a line making Merlin IIIs or XIIs could not. But they could make Merlin 45s with less trouble.
There seems to be an intermediate section between the crankcase proper and the supercharger which is where a number of "accessories" are located, like magnetos, starter motors,, generators and some odd pumps (hydraulic, vacuum etc) perhaps it is the tooling for this section which is different?
This may also be the difference between Packard engines and British engines as Packard used a different supercharger drive/shift mechanism.
The Merlin XX and 45 used the same supercharger (at least internal and front cover/inlet)
The main point, which we are loosing sight of, is that the Merlin XX made 1175hp at 20,500ft compared to the 840-850hp (?) the early Allison made at the same/similar altitude, which would obviously affect the performance at 20,000ft and above.
The Merlin 61 was rated at 1390hp at 23,500ft which really explains the difference between an Allison Mustang and a Merlin Mustang.
Data sheets:
-one
-two
-three
Each of whom state service (not absolute, that is higher) ceiling of 33000-34000 ft, depending on the weight. The 2-speed variants of the Merlin 30s series not differing from 20 series in power vs. altitude.
Not the case if you can't state so many hundreds of after action reports that prove your point.
If I'm not mistaking it badly, the power figure of 1175 HP at 20500 ft is from provisional charts/tables? It can be seen, however, on the Hurricane IIa data sheet. The power chart (here) shows 1175 HP at 17500 ft, or 1060 HP at 20000 ft, the Packard Merlin table giving the similar power vs. height value (1120 HP at 18500 ft; unfortunately listed under 'with ram' coulmn, instead of under 'without ram').
Merlin 60/61/62 (we can se how the Merlin 61 was utter crap):
Specific airplanes that went through climbing trials with a similar take-off weight:
P-39N No. 42-4400
(Allison V-1710-85)
auw 7,274 lbs.
38,500 ft (service ceiling)
P-40N No. 42-9987
(Allison V-1710-81)
auw 7,413 lbs.
38,200 ft (service ceiling)
Hurricane II No. Z3564
(Rolls Royce Merlin XX)
auw 7,397 lbs.
35,900 ft (service ceiling)
Spitfire XII No. DP845
(Rolls Royce Griffon VI)
Clipped Wings
auw 7,320 lbs.
37,300 ft (service ceiling)
Seafire III No. LR765
(Rolls Royce Merlin 50)
auw 7,100 lbs.
35,600 ft (service ceiling)
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Shortround6
Major General
I would note that trying to compare the service ceiling different aircraft to determine how good or bad the engine was ignores several other factors.
Two of which are lift and drag. to show how these can screw things up the Spitfire with a Merlin III had a higher ceiling than than Hurricane with a Merlin III
same engine even if the weights were only a few hundred pounds apart. Hurricane had a slightly larger wing, 258 sq ft vs 242 and should have had more lift. (air foils were NOT the same) but the higher drag sucked up more of the power.
I would also be a bit suspicious of the P-39 and P-40 as those are abnormally low weights for them. The P-40 for example having only four guns with 235rpg. Fuel load is unspecified but as this was sort of a prototype of the P-40N (plane was actually a P-40K) the forward wing tank may not be present. The engine may or may not have an electric starter.(first few hundred P-40Ns did not) and they used a much smaller battery than the planes with electric starters.
Two of which are lift and drag. to show how these can screw things up the Spitfire with a Merlin III had a higher ceiling than than Hurricane with a Merlin III
same engine even if the weights were only a few hundred pounds apart. Hurricane had a slightly larger wing, 258 sq ft vs 242 and should have had more lift. (air foils were NOT the same) but the higher drag sucked up more of the power.
I would also be a bit suspicious of the P-39 and P-40 as those are abnormally low weights for them. The P-40 for example having only four guns with 235rpg. Fuel load is unspecified but as this was sort of a prototype of the P-40N (plane was actually a P-40K) the forward wing tank may not be present. The engine may or may not have an electric starter.(first few hundred P-40Ns did not) and they used a much smaller battery than the planes with electric starters.
wuzak
Captain
Note that the Merlin 50 had the same 10.25" supercharger impeller as the XX, but ran a lower speed ratio than the XX in FS gear - 9:0:1 vs 9:49:1.
That means that the XX has higher altitude capability than the Merlin 50.
The Merlin 50 has to balance low altitude performance vs altitude performance. The XX had less of a compromise due to the low gear.
Type of wing guns has nothing to do with engine performance.
You seem suspicious of any facts that run afoul of this ongoing Merlin XX what-if fantasy.
No P-51s were built with the Packard Merlin XX because the P-40F did not exactly deliver thrills.
Many, if not most, British made aircraft evaluated by the A&AEE were prototypes.
Results from specific government tests are more helpful than generic figures that are claimed to be
estimates from the makers.
Engine graphs are interesting and also a red flag when the data does not correlate with flight testing.
Seafires tended to be slower than Spitfires with the same engine, but if loaded weight were adjusted there was no significant change in ceiling if going from a Merlin 50 to a standard Spit Five engine:
Spitfire VC No. AA873
(Rolls Royce Merlin 45)
auw 6,917 lbs.
36,400 ft (service ceiling)
Spitfire VC No. AA878
(Rolls Royce Merlin 45)
auw 6,965 lbs.
36,500 ft (service ceiling)
Service ceiling:
P-40E: 30600 ft
P-40F: 34300 ft
Speed at 20000 ft:
P-40E: ~320 mph
P-40F: 350-360 mph
All despite the P-40F was heavier by 300 lbs. Thus it looks to me that there was improvement once the V-1650-1 was installed on the P-40. The P-40F predate the 6-gun, compete-fuel version of the P-40N by a year. That was credited with 325-340 mph at 20000 ft, and service ceiling of 31000 ft
P-40E: 30600 ft
P-40F: 34300 ft
Speed at 20000 ft:
P-40E: ~320 mph
P-40F: 350-360 mph
All despite the P-40F was heavier by 300 lbs. Thus it looks to me that there was improvement once the V-1650-1 was installed on the P-40. The P-40F predate the 6-gun, compete-fuel version of the P-40N by a year. That was credited with 325-340 mph at 20000 ft, and service ceiling of 31000 ft
wuzak
Captain
The Merlin 45 had the same supercharger impeller and gear ratio as the 50. They had the same power ratings.
The Merlin 46 had a larger supercharger and had a higher ceiling in the Spitfire.
wuzak
Captain
Rolls-Royce seriously considered installing a Merlin XX into a Mustang I at the time they were doing the Mustang X conversion. The conclusion was that the Merlin 61 gave much better performance and that making the Merlin XX version would be a dilution of effort for a much smaller performance improvement.
The Merlin 61 had been in testing for a while and the Spitfire IX was entering production when the discussions on the Mustang X were being held. The Spitfire IX was entering service about the time the Mustang X was being converted and its first flight.
wuzak
Captain
You mean to say the contemporary P-40 had a lower ceiling than the Spitfire V?
That is no wonder.
It wasn't until this thread started, my head hurts.
Shortround6
Major General
You are correct, type of wing guns has little to with engine performance
however weight of the guns (and ammo) has a very noticeable and measurable affect on performance of the aircraft.
Ceiling is a measure of aircraft performance not engine performance.
Strip enough weight out of an aircraft and you can increase the ceiling by thousands of feet with no change to the engine.
And that is what your examples of the P-39 and P-40 are doing, running hundreds hundreds of pounds lighter than the normal combat versions.
They only built about 200 of the light weight P-40Ns and after they were in service the units operating them often installed the electric starters and bigger batteries, they often added the forward fuel tank back in too, finding the 120 gallons of internal fuel too limiting. Likewise the lightweight P-39s with only 87 US gallons were found to be to limited in service and retrofit kits were issued to bring them back up to the standard 120 gallons.
I happen to like facts but I Like my facts applied equally and not cherry picked. The P-40F did deliver some thrills. at altitudes over 20,000ft it was 30-40mph faster than a P-40E. The P-40N prototype you quote figures for is not only 1000lbs lighter than a standard P-40F with Merlin it it is almost 800-900lbs lighter than vast majority of P-40Ns.
I actually think that the Merlin XX in the Mustang was not that great an Idea as the amount of time and effort to get it to work is not worth the result, not so much in performance but in the sense that you just have to do it all over again (and build new jigs and fixtures) to get the two stage engine in the Mustang.
The difference in timing being around 1/2 a year.
Think it would've been fair to note that installation of the V-1710 (and V-1650-1 for that matter) on the P-39/40/51 was better than it was the case with 1-stage Merlins installed on Hurricanes and Spitfires, due to having a better carb and less draggy exhausts, that were probably also less restrictive. Better carb, once installed on the Spitfire, gave 10 mph. So once at 30000 ft and above, benefits of better installation should be outweighting the benefits of several HP extra the particular engine can provide.
Depends on when the project is started. If the V-1650-1 powered Mustang is produced instead of the A-36 that would meant the USAF has a viable LR fighter for the ETO by Spring of 1943. Leaves plenty of time to escort bombers over Germany, saving 8th bombers and giving the LW bloody nose.
Depends on when the project is started. If the V-1650-1 powered Mustang is produced instead of the A-36 that would meant the USAF has a viable LR fighter for the ETO by Spring of 1943. Leaves plenty of time to escort bombers over Germany, saving 8th bombers and giving the LW bloody nose.
