Was the De Havilland Mosquito a good fighter?

cocky pilot · Jan 2, 2011

FLYBOYJ said:
Just curious - what's your source for that???

Flyboy

It is the common narrative for the mosquito based on the weight wetted area thrust and other factors. It was twice the weight twice the power and twice the wetted area but had radiators in the wing leading edge, a mid wing configuration which was theoretically better than a spitfires low wing and had a laminated wood finish which didnt have rivets (even flushed ones). I am not an aerodynamacist but I dont have to be. The air ministry didnt believe the claims and it was panned on the other side of the pond too. Nobody believed the claims until they were proved.

It is easy to overstate claims for an airplane, the Mosquito gave the luftwaffe a big surprise when introduced. There are so many marques that it is difficult to compare one with another and same for its adversaries but generally it required the best of the luftwaffes planes to intercept it throughout its career. Towards the end nitrous oxide powered 109s and Me262s had a clear speed advantage but before that the best interceptors didnt. 30/50 MPH is a decisive advantage in a combat but it is the absolute minimum required to intercept, bearing in mind the range of radar at the time and the number of airfields. In WW2 BoB terms the mosquito was as fast as as a JABO 109 but had the bomb load of a Ju88.

I found this which I found interesting. The various Merlin engines are often quoted for BHP/altitude I didnt realise the weight changed considerably
from
Scoopless Mustang
The Story of Anson Johnson's Race 45 and Where it is Now

With no funds left, Johnson went back to Miami to come up with a program to improve his aircraft's speed. In his mind, he knew he had the proper aircraft, but the -3 Merlin wasn't the optimum engine for racing. After some research, Johnson sought out and bought a Merlin -225, a lighter version of the engine normally found on the de Havilland Mosquito. The -225 was a single stage, dual speed blower Merlin with a 1,620 hp rating at 3,000 rpm. It was also 240 pounds lighter that the 1,380 hp dual stage -3 Merlin. Other engine modifications were made to increase horsepower. Johnson was well on his way in the quest for speed.

also discussing the mosquito aerodynamics I found this
Airplane aerodynamics and performance By Jan Roskam, Chuan-Tau Edward Lan

FLYBOYJ · Jan 2, 2011

cocky pilot said:
Flyboy

It is the common narrative for the mosquito based on the weight wetted area thrust and other factors. It was twice the weight twice the power and twice the wetted area but had radiators in the wing leading edge, a mid wing configuration which was theoretically better than a spitfires low wing and had a laminated wood finish which didnt have rivets (even flushed ones). I am not an aerodynamacist but I dont have to be. The air ministry didnt believe the claims and it was panned on the other side of the pond too. Nobody believed the claims until they were proved.

It is easy to overstate claims for an airplane, the Mosquito gave the luftwaffe a big surprise when introduced. There are so many marques that it is difficult to compare one with another and same for its adversaries but generally it required the best of the luftwaffes planes to intercept it throughout its career. Towards the end nitrous oxide powered 109s and Me262s had a clear speed advantage but before that the best interceptors didnt. 30/50 MPH is a decisive advantage in a combat but it is the absolute minimum required to intercept, bearing in mind the range of radar at the time and the number of airfields. In WW2 BoB terms the mosquito was as fast as as a JABO 109 but had the bomb load of a Ju88.

I found this which I found interesting. The various Merlin engines are often quoted for BHP/altitude I didnt realise the weight changed considerably
from
Scoopless Mustang
The Story of Anson Johnson's Race 45 and Where it is Now

With no funds left, Johnson went back to Miami to come up with a program to improve his aircraft's speed. In his mind, he knew he had the proper aircraft, but the -3 Merlin wasn't the optimum engine for racing. After some research, Johnson sought out and bought a Merlin -225, a lighter version of the engine normally found on the de Havilland Mosquito. The -225 was a single stage, dual speed blower Merlin with a 1,620 hp rating at 3,000 rpm. It was also 240 pounds lighter that the 1,380 hp dual stage -3 Merlin. Other engine modifications were made to increase horsepower. Johnson was well on his way in the quest for speed.

also discussing the mosquito aerodynamics I found this
Airplane aerodynamics and performance By Jan Roskam, Chuan-Tau Edward Lan

All great info CP and I'm aware of the shock the Mosquito gave the Luftwaffe at its introduction as you had an aircraft flying over Germany that couldn't be intercepted "at a standing start." If you do look at the speeds of the first Mosquitoes, they were fast, very fast, but there were aircraft capable of catching the aircraft 1. Depending if it was already airborne and had good vectors to perform a proper intercept and 2., the model of the Mosquito (which it seems the PR was really the one that gave the Luftwaffe worries as it was the lightest and fastest model of the early mosquitoes), so I think we have to put into perspective which model and what time frame to really substantiate the 30 mph claim. The fastest speeds of the Mosquito (which would have substantiated this claim) were recorded by the prototypes.

Jabberwocky · Jan 3, 2011

FLYBOYJ said:
Understand that when a Mosquito was carrying a 4000 pound bomb, it wasn't flying close to 400 mph either.......Or 300 mph...

The experience of the LNSF (8 Group) contradicts this.

They observed that the Mk XVI with a 4000 lbs cookie in the bomb bay achieved a maximum speed of 408 mph inbound to the target and 419 mph outbound from the target (See Sharpe and Bowyer).

The same aircraft could cruise continuously above 350 mph TAS, fully loaded with a 4000 lb bomb and external tanks, when above 25,000 ft.

Range cruise was conducted at 230-270 mph ASI, depending on distance to target. 230 mph ASI at 25,000 ft would give a TAS of about 295 mph. 250 mph would give 315 mph, 270 mph would give a TAS of 340 mph.

Glider · Jan 4, 2011

I don't know the exact performace of the Mk XVI but I do know that the Mk IX at max overload weight with two 500lb bombs mounted externally had a max speed of about 390mph. With this in mind, 400mph plus certainly sounds feasible on the more powerful Mk XVI with an internal 4,000lb bomb and without the drag of the eternal bombs

FLYBOYJ · Jan 4, 2011

Jabberwocky said:
The experience of the LNSF (8 Group) contradicts this.

They observed that the Mk XVI with a 4000 lbs cookie in the bomb bay achieved a maximum speed of 408 mph inbound to the target and 419 mph outbound from the target (See Sharpe and Bowyer).

The same aircraft could cruise continuously above 350 mph TAS, fully loaded with a 4000 lb bomb and external tanks, when above 25,000 ft.

Range cruise was conducted at 230-270 mph ASI, depending on distance to target. 230 mph ASI at 25,000 ft would give a TAS of about 295 mph. 250 mph would give 315 mph, 270 mph would give a TAS of 340 mph.

Depending on "where or when" on your numbers proves my point.

What really mattered in the end is the speed they were able to "safely" open their bomb bay doors.

Shortround6 · Jan 4, 2011

FLYBOYJ said:
Depending on "where or when" on your numbers proves my point.

What really mattered in the end is the speed they were able to "safely" open their bomb bay doors.

Going back to posts 101,104 and 107 you stated that the speed limitation for opening the doors was 305 knots and also stated that this was indicated airspeed.
I believe that 305 knots works out to 350mph at sea sea level ?
350mph IAS at sea level works out to what true airspeed at 25,000ft ?

Now the accuracy may have been terrible, there may have been a problem with bomb separating from the aircraft at high speed but it doesn't look like the bomb door speed limitation would be much of a problem in level flight to me.
Am I missing something?

FLYBOYJ · Jan 4, 2011

Shortround6 said:
Going back to posts 101,104 and 107 you stated that the speed limitation for opening the doors was 305 knots and also stated that this was indicated airspeed.
I believe that 305 knots works out to 350mph at sea sea level ?
350mph IAS at sea level works out to what true airspeed at 25,000ft ?

Now the accuracy may have been terrible, there may have been a problem with bomb separating from the aircraft at high speed but it doesn't look like the bomb door speed limitation would be much of a problem in level flight to me.
Am I missing something?

Yes you are - as you mentioned just because you can open the doors at the speeds indicated in the Pilot's Notes doesn't mean you're going to bomb at those speeds. That's just a limitation placed on the airframe. I don't have data on bomb delivery speeds but I doubt they are going to be close to those mentioned speeds. But 350 mph IAS would vary depending on airpressure and temperature. Also consider winds aloft, but it would be higher than 350 mph.

drgondog · Jan 4, 2011

Shortround6 said:
Going back to posts 101,104 and 107 you stated that the speed limitation for opening the doors was 305 knots and also stated that this was indicated airspeed.
I believe that 305 knots works out to 350mph at sea sea level ?
350mph IAS at sea level works out to what true airspeed at 25,000ft ?

Now the accuracy may have been terrible, there may have been a problem with bomb separating from the aircraft at high speed but it doesn't look like the bomb door speed limitation would be much of a problem in level flight to me.
Am I missing something?

SR - at 25,000ft the IAS would be 234mph for a TAS of 350mph for STP and no head/tailwinds

it varies as the Sqrt(RHOalt/RHOsl) which for 25K is .6698

I forgot - the stagnation pressure at 350mph TAS at 25,000 feet is ~ 140 psf - obviously a high Q load. I have zero idea what the Mossie restrictions were for their bomb bays but they sure didn't want to lower gear or flaps in that range..

Note - this is an airspeed where incompressible flow theory starts to break down and the ridiculous claims of "I was doing 650mph chasing the bugger' were due to serious side effects of comprssible flow on pitot tube/instrument readings

But I am sure you already knew that..

FLYBOYJ · Jan 4, 2011

Bill, the human...

drgondog · Jan 4, 2011

FLYBOYJ said:
Bill, the human...

Oh no, Joe - that device was the greatest aviation supplement until Global Nav. I lost that, my logbook and bunch of other stuff in a fire a long time ago.

DougE · Apr 22, 2011

I know next to nothing about aircraft, but my dad, who turns 90 this year, flew as navigator on Mosquitos out of Harrington on missions for the OSS as part of Operation Red Stocking. He swears by this plane which they took to 30,000 feet on night runs over Germany and France. He flew in other bombers as well, but clearly felt this was an extraordinary machine. I'll point him to this forum and he can explain why himself.

A4K · Apr 22, 2011

Be great to hear what he has to say DougE! (Welcome to the forum too!)

barney · May 1, 2011

Pilot's Notes - De Havilland Mosquito FB 6

mhuxt · May 5, 2011

DougE said:
I know next to nothing about aircraft, but my dad, who turns 90 this year, flew as navigator on Mosquitos out of Harrington on missions for the OSS as part of Operation Red Stocking. He swears by this plane which they took to 30,000 feet on night runs over Germany and France. He flew in other bombers as well, but clearly felt this was an extraordinary machine. I'll point him to this forum and he can explain why himself.

Hiya,

<S> to your Dad. If he's not already done so, see if he's willing to share his experiences with a fellow named Norman Malayney, who is the most enthusiastic and faithful chronicler of the USAAF Mosquito effort.

You can find him at The Mosquito Page (see the forum page), or I can give you his email if you like.

Was the De Havilland Mosquito a good fighter?

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