Mosquito Low on Power

[VampireNZ]

Refer to notes from this pilot flying a restored FB26 with RR Merlin 25 engines installed. (Canadian version of the Mk. 6)

 

Takeoff - Keith mentions he takes off at 0 Boost for a smooth straight takeoff. Try that in DCS and you will be lucky to see over 100 MPH!

Cruise - Their usual cruise settings are  +4 Boost @ 2400rpm = 260mph cruise. Again, try that in DCS at a low level cruise +4 @ 2400rpm and you will get 235mph cruise...+ warning horn constantly.

Also he notes they don't take her over +13 boost, and later mentions this is good for 320mph. Again - DCS +13 will get you 295mph at most.

30 mph might not sound like a huge amount, but the Mozzie seems to be really struggling to see the performance or speed it was famous for. Would be really nice if she got a tune-up at some point. Would be nice to see her getting along at the 300+ in high-boost cruise like she is supposed to.
 

[Holbeach]

@VampireNZ

 

"Takeoff - Keith mentions he takes off at 0 Boost for a smooth straight takeoff."

He actually says, 13 boost is T/O.

Start at 0 then increase to 13 boost for a straight T/O. Easily achieved with our Mossie.

He doesn't say at what weight this museum aircraft is at, but they are usually lighter that a WWII fit..

..

Edited February 10 by Holbeach

[VampireNZ]

36 minutes ago, Holbeach said:

VampireNZ

 

"Takeoff - Keith mentions he takes off at 0 Boost for a smooth straight takeoff."

He actually says, 13 boost is T/O.

Start at 0 then increase to 13 boost for a straight T/O. Easily achieved with our Mossie.

He doesn't say at what weight this museum aircraft is at, but they are usually lighter that a WWII fit..

..

He actually says "30 inches of boost" - which is actually +0 lbs boost on the gauge, which is about 30 inches of mercury or one atmosphere (29.92inhg). So he just used the inches figure instead of the pounds figure for boost we are used to.  He also doesn't say anything even close to "Start at 0 then increase to +13 boost for a straight T/O".

Regarding weight - they usually don't fly with 10% fuel either, which is what I used and nil stores at all. So just a bit of extra radio gear maybe, but most restored aircraft have this stuff installed for historic reasons. It obviously has the cannons installed etc. - again I used nil gun ammo. FYI it is not a 'Museum' aircraft either.

Also, may I ask why you thought it necessary to post a link to my profile?

Edited February 10 by VampireNZ

[Nealius]

  

1 hour ago, VampireNZ said:

30 inches of mercury or one atmosphere (29.92inhg)

"in" is inches, "hg" is mercury. 30 and 29.92 are not the same value. 

1 hour ago, VampireNZ said:

+0 lbs boost on the gauge, which is about 30 inches of mercury

Only if outside baro pressure is 30.00. +0 indicates no additional pressure added to atmospheric pressure.

Edited February 10 by Nealius

[Holbeach]

2 hours ago, VampireNZ said:

He actually says "30 inches of boost" - which is actually +0 lbs boost on the gauge, which is about 30 inches of mercury or one atmosphere (29.92inhg). So he just used the inches figure instead of the pounds figure for boost we are used to.  He also doesn't say anything even close to "Start at 0 then increase to +13 boost for a straight T/O".

Regarding weight - they usually don't fly with 10% fuel either, which is what I used and nil stores at all. So just a bit of extra radio gear maybe, but most restored aircraft have this stuff installed for historic reasons. It obviously has the cannons installed etc. - again I used nil gun ammo. FYI it is not a 'Museum' aircraft either.

Also, may I ask why you thought it necessary to post a link to my profile?

He actually says, 0 boost/30 inches, on the brakes, release brakes and increase power to 13 inches, (slip of the tongue), which is 56/58 inches, a hell of a lot of power.

..

Edited February 10 by Holbeach

[Skewgear]

I'd expect their aircraft is much lighter than a wartime one. But the DCS Mossie is also on the bottom of the observed variation in speeds from Mosquito FB.VI test flights.

I have thought for a while, though, that our Mossie is under powered. Single engine flight is borderline dangerous even at cruising speeds, whereas one modern Mossie operator cheerfully makes cockpit videos showing one engine shut down and feathered in flight.

[NineLine]

On 2/9/2025 at 7:29 PM, VampireNZ said:

Refer to notes from this pilot flying a restored FB26 with RR Merlin 25 engines installed. (Canadian version of the Mk. 6)

 

Takeoff - Keith mentions he takes off at 0 Boost for a smooth straight takeoff. Try that in DCS and you will be lucky to see over 100 MPH!

Cruise - Their usual cruise settings are  +4 Boost @ 2400rpm = 260mph cruise. Again, try that in DCS at a low level cruise +4 @ 2400rpm and you will get 235mph cruise...+ warning horn constantly.

Also he notes they don't take her over +13 boost, and later mentions this is good for 320mph. Again - DCS +13 will get you 295mph at most.

30 mph might not sound like a huge amount, but the Mozzie seems to be really struggling to see the performance or speed it was famous for. Would be really nice if she got a tune-up at some point. Would be nice to see her getting along at the 300+ in high-boost cruise like she is supposed to.
 

Can you supply a track, can you determine if the fuel load is the same as the video, etc for take off?

I will note that what you suggest is very much below what is suggested in the manuals, I am not sure a civilian restored Mossie is the best reference. 

[grafspee]

On 2/10/2025 at 10:31 AM, Nealius said:

  

"in" is inches, "hg" is mercury. 30 and 29.92 are not the same value. 

Only if outside baro pressure is 30.00. +0 indicates no additional pressure added to atmospheric pressure.

30inch of mercury and 29.92 inch of mercury is about the same.

Boost gauge in mosquito and in spitfire  is absolute pressure gauge only scaled in different manner, 0 means what ever they set up to be and it won't change with outside pressure.

If you are flying at 20k ft and gauge say 0 that does not mean that pressure in manifold is exact the same as pressure outside if this gauge shows 0 it means that in manifold pressure there is around 30 inch of mercury.

If engine is off that gauge will show actual pressure, needle will be slight below 0 boost if outside pressure is below standard atm and slight above if outside pressure is slight above.

[Bozon]

16 hours ago, grafspee said:

30inch of mercury and 29.92 inch of mercury is about the same.

Boost gauge in mosquito and in spitfire  is absolute pressure gauge only scaled in different manner, 0 means what ever they set up to be and it won't change with outside pressure.

If you are flying at 20k ft and gauge say 0 that does not mean that pressure in manifold is exact the same as pressure outside if this gauge shows 0 it means that in manifold pressure there is around 30 inch of mercury.

If engine is off that gauge will show actual pressure, needle will be slight below 0 boost if outside pressure is below standard atm and slight above if outside pressure is slight above.

Really? Thanks for the info. I always assumed that it actually measures the difference between the manifold and ambient static pressure.

What you are saying makes more sense from perspective of engine performance. I just thought there is some other advantage to measuring relative pressure that I was not aware of.

[Terry Dactil]

 

9 hours ago, Bozon said:

 I always assumed that it actually measures the difference between the manifold and ambient static pressure.

What you are saying makes more sense from perspective of engine performance. I just thought there is some other advantage to measuring relative pressure that I was not aware of.

Me too. It can't be absolute pressure 'cause it would show around 15 psi at sea level and negative values mean it's sucking and that's not how engines work. 

Easy enough to check though. Let's go up to 18,000 feet where the air pressure is about half that at sea level, shut down an engine an see what the boost gauge says then.

Here we are at 18,000 feet.

 

Well bugger me! It shows about minus 7 psi now,   That's the difference from around sea level and not from ambient as I thought.

Thanks grafspee. You made my day! Live and learn!

 

 

Edited May 17 by Terry Dactil