Irregularity in the Mosquito's reported climb rate.

[Karnak]

Can anybody explain why the Mosquito B.MkIV has an initial climb rate of 2,880 ft per minute with engines rated at 1,230hp engines and a weight of 21,800lbs while the Mosquito FB.MkVI only has an inital climb rate of 1,870ft per minute with engines rated at 1,635hp and a weight of 22,500lbs?

It seems to me that the Mosquito FB.VI should climb at least as fast, if not faster, than the Mosquito B.IV.  The FB.VI's much more powerful engines should more than make up for the extra 500lbs.

Every source I look at gives them this kind of climb rate.

If we look at the P-38L we see that it gets  2,850ft per minute on 1,600hp engines while weighing 21,600lbs.

All this leads me to think that at some point a typo occured in the reporting of the climb rate of the Mosquito FB.VI and that has propagated down through all of the newer sources.  I think that the FB.VI probably had an initial climb rate of about 2,870ft per minute.

It doesn't make sense any other way.

Can somebody shed some light onto this for me?

[F4UDOA]

Karnak,

What I have found to be the most difficult thing about A/C performance is finding accurate data. You may be looking at what you think is a reputable writer but let me tell you there are with few exceptions any accurate books written from actual test data. Most are reprints of reprints and the writer doesn't know if it's combat power or what loading condition or if the plane had a pilot.

What I reccomend is to do what I did. Find the source document. For your search is actually quite easy since your Government has more AFDU test ready for you than any branch of the US military. Just go to

PROCAT doc service

Click the search catalogue tab and type in Mosquito. You will get all of the test docs for the British Air Ministries. Then order them for 5 Dollars(Pounds) per Doc and in a few weeks you will have the actual data in your hand.

What you will probably find out is the the later version of the Mossy was a better climber. Just a hunch.

Thank me later<S>

BTW, at first glance there wer over 300 Docs for the Mosquito listed.

[funkedup]

Looking at the weight and power, 2800 fpm seems about right for a maximum sustained climb rate.  The lower figure was probably one of the following:
1.  Averaged figure, i.e. altitude divided by time-to-climb.
2.  Figure obtained with less than maximum power.  
3.  Figure obtained with external/internal ordnance or drop tanks.

The last two are pretty common for AFDU or RAE.

[Zigrat]

2880 fps is way to high for a 22,000 lb aircraft with 2 1200 hp engines

wayyyy too high as in not possible

[funkedup]

Yeah, 2200 is more like it for the B. Mk. IV.  Again, you gotta know altitude/loading/config/power setting for a quoted climb rate to be useful.

[Karnak]

I have seen those numbers from numerous sources.

On difference is that the Mosquito B.MkIV is sometimes listed as having 1,480hp Merlin 23s instead of the 1,230hp Merlin 21s.  In other words that could be the initial climb rate of late B.MkIVs.

_____________________________ _____________________________ _____________________________ ______________________

I have to admit that I am a bit concerned about the fact that the AH Mossie has ducted saxophone exhausts.  The serve no function in AH and seriously reduce the performance of the aircraft.  The top speed is dropped by 14mph because of the lack of exhaust thrust from the engines.  14mph will make the difference between outrunning an N1K2 or not. If the performance degradation from the ducted saxophone exhausts is modeled the Mossie will have a far harder time surviving in the MA.

[juzz]

I have found an original source(Report No. A&AEE/767. "Mosquito W4050(2 Merlin XXI engines). Preliminary Performance and Handling Trials". 3 March 1941), quoted in a book which happens to list that 2880fpm climbrate.

It is for the first prototype(W 4050) at an AUW of 16,770lbs and with Merlin 21 engines.

 

The best rate of climb in M.S. blower is 2880 feet/min. at 11,400 feet and in F.S. blower is 2240 feet/minute at 18,100 feet.

Hmmm, a coincidence?