DH Mosquito cockpit diagrams

[Bergerie1]

I am trying to help a friend to understand the carburettor heat controls on the DH Mosquito Mk FB40, an Australian built version designated A52-24, which I believe may have been fitted with Packard built Merlin engines. Does anyone have a picture or annotated cockpit diagram of the engine controls and carb heat controls which has a clear depiction of these controls? I would be very grateful for any help from knowledgeable PPRuNers. Many thanks in advance.

[Jhieminga]

I haven't tried registering, but according to the website a free account will get you access to a few sets of Pilot's Notes here: https://www.avialogs.com/aircraft-d/de-havilland/itemlist/category/287-dh-98mosquito There is a US version included which might give you the different viewpoint you're looking for.

[Herod]

Try the DH Museum in UK. https://www.dehavillandmuseum.co.uk/ A small museum, but with excellent staff and THREE Mossies, including the prototype

[Jhieminga]

As far as a quick check of Wikipedia can show me... the Australian built Mossies used the Merlin 31 which appears to have been a Rolls-Royce built version. Packard did build a Merlin 28 based version as the V-1650-1 but that was not a Mosquito engine, or does not appear to have been one. Other sections of the relevant pages do mention a Packard-built Merlin 31 variant though. The upshot of this is that the Aussie Mossie most likely had carb heat controls (and other engine controls) that matched other Mosquito versions but I cannot be 100% sure. Can somebody check the relevant Putnam book? 😉

[Bergerie1]

Thanks Jelle. The only reference I found was on page 14 where it mentions carburettor heat, if fitted. I would have thought carb heat was a rather important feature, so why, if fitted?
https://www.avialogs.com/aircraft-d/de-havilland/item/8501-ap2019e-l-t-pilots-notes-for-mosquito-fbvi-fb26

[DHfan]

Putnam says the first 100 had Packard-Merlin 31s and the remaining 112 had Merlin 33s, but doesn't state whether R-R or Packard. Personally I would think Packard are more likely than shipping R-R engines 12,000 miles or so,

[Jhieminga]

I would have thought carb heat was a rather important feature, so why, if fitted?
The Merlin uses an injection carb. On those, you generally do not need carb heat, on some installations you only have an alternative air intake. Depending on the specific type, you may or may not have a venturi in the carburettor. If there is a venturi present, the fuel is injected further downstream and all of this severely reduces the chance of carb icing. Location of the carb on the engine and the specifics of the intake path that leads to it may also determine the need to use any form of heating. It can be different between various engine installations. The Mosquito was developed into such a variety of models for different roles, I can imagine this being more of an issue for a high-flying PR variant than for a low-level ship-buster.

I have only encountered a carb heat control on piston engines that use a normally aspirated carburettor. On fuel injected engines, sometimes you can have an alternative air control, sometimes this is covered by a spring-loaded flap in the intake manifold and there is no lever for the pilot to actuate it.

If you would like to know more:
https://www.enginehistory.org/Accessories/HxFuelSys/FuelSysHx08.shtml
https://www.enginehistory.org/Accessories/HxFuelSys/FuelSysHx09.shtml

[GeeRam]

Putnam says the first 100 had Packard-Merlin 31s and the remaining 112 had Merlin 33s, but doesn't state whether R-R or Packard. Personally I would think Packard are more likely than shipping R-R engines 12,000 miles or so,

I don't believe Packard built a version of the Merlin 31 or Merlin 33, so I would say all had RR engines.

[DHfan]

Mosquito by C. Martin Sharp and Michael J. F. Bowyer states Packard-Merlin 31s and Packard-Merlin 33s.

[jonkster]

This may or may not be relevant - I cannot speak about the Mosquito but with the Lancaster it was referred to as the "carburettor air-intake heat control"

All 4 engines were controlled by a single lever that had 3 positions, cold, warm and hot (or on some earlier versions just cold and warm). May be worth searching for "carburettor air-intake" or "air intake control" rather than carburettor heat?

[EXDAC]

I have a set of pilot notes for the Mosquito TIII (Merlin 21 or 23 engines). They are a copy of an Air Ministry document dated August 1943. I was not able to find any reference to carburettor heat or anything similar. Probably not related to the model in question.

[dduxbury310]

Most Canadian and Australian-built Mosquitos were factory-fitted with Packard Merlins at their relevant factories, courtesy of Lend-Lease, either model 31s or 33s.

[DHfan]

I don't believe Packard built a version of the Merlin 31 or Merlin 33, so I would say all had RR engines.

Not only did they make them, it's the only place they were made.

I remembered that the FB.VI should have a Merlin 2x, but couldn't recall exactly which until I looked it up. Packard-Merlin 31 and 33s were the equivalent of Rolls-Royce Merlin 21 and 23s.

Re the Lancaster carb heat settings. The Mosquito FB.VI was a relatively low-altitude daylight variant. Would carb heat be relevant?

[sycamore]

Ref the FB 6 and FB 26 PN..page 14,para 25,highlighted,covers `Carburettor De-icing(Mk26 when fitted); each engine had a 9.5 gal tank and pump,to pump alcohol into the carb.in icing,or de-ice the carburettor,at 2-2,5 gph (lo) or 7.5gph on Hi setting...

[megan]

trying to help a friend to understand the carburettor heat controls on the DH Mosquito Mk FB40There are none in the Australian built Mosquitos as they used the Packard 31 & 33 engines.

British built engines had two barrel SU carburetors which were apparently subject to icing, hence jonkster's comment about the Lancaster being so fitted with icing controls, as was the Lancastrian and Merlin Beaufighter, but oddly Spitfire and Hurricane manuals make no mention of carb heat. Perhaps because the the SU carburettors prevented carb icing by having hot engine oil fed inside the carb throttle plates and hot engine coolant was circulated around the choke tubes. These arrangements were effective to prevent carb icing but, incurred wasteful heating of the intake charge and the additional oil and coolant circuits were unwanted vulnerabilities that could contribute to engine failure.

Packard engines used a Bendix-Stromberg pressure carburettor which injected the fuel into the eye of the supercharger, thus avoiding icing issues.

[Bergerie1]

Megan, Thank you very much for that information. I will get back to you.

[Octane]

Email the company in Auckland, NZ that has restored 3 Mossies to airworthiness. Avspecs?

[megan]

The Mrerlin was built in many variants, some being applicable to only one aircraft type, see NOTE (2) regarding allocation of Mark numbers.


https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/2000x1869/rr001_1d0ef29b25575ffa76d2a9786abd157eba3360bc.jpg
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1200x2000/rr002_3455fe07f36e2c7b17479e3e9a4792bc380d0cc1.jpg

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/1988x1619/rr004_97a8437cc5b147793461bdbd52e66404fd3baa51.jpg



Commercial Merlin versions. Some warbird operators are fitting commercial Merlins because of their beefed up components.

Merlin 500 series: Two Speed - Single Stage Supercharger

Identical to Merlin T24-2 but termed Merlin 500 for Civil or Commercial operator

500 B.O.A.C. Lancastrian York

500-2 B.S.A.A. Lancastrian York

500-3 Alitalia Lancastrian

500-4 Skyways Limited Lancastrian York

500-5 F.A.M.A. Lancastrian York

500-6 Silver City Airways Lancastrian

500-20 Fiat G.59

500-21 Flight Re-Fuelling Ltd Lancastrian

500-23 Egyptian Government Lancastrian

500-29 CASA C.2111

500-45 Hispano HA-1112

501 T.C.A. Lancastrian

502

502-1 B.O.A.C. York

504 No Production

530 No Production

539 No Production

549 No Production

Merlin 600 series: Two Speed - Two Stage Supercharger

600 Tudor Prototype (Converted to Merlin 102A)

604 Argentine Government

620 T.C.A. & RCAF D.C.4 M.1

621-1 B.O.A.C. Tudor II

621-2 B.S.A.A. Tudor II, IV, V

621-5 Flota Aerea Mercante Tudor

621-15 Argentine Government Lincoln

622 T.C.A. (Domestic) D.C.4 M.2

623-2 B.S.A.A. Tudor IV

624-10 T.C.A. (Atlantic) D.C.4 M.2

625 No Production

626-1 B.O.A.C. Canadair IV C.4

626-12 Canadian Pacific Canadair IV C.4

630 No Production

631 No Production

640 No Production

641 No Production

Merlin 700 series: Two Speed - Two Stage Supercharger

724-1 B.O.A.C. Similar to Merlin 626-1 with cooling mod.

724-1C B.O.A.C. As Merlin 724-1 with crossover exhaust

722-10 Canadair As Merlin 622-10 with cooling mod.

724-10 Canadair As Merlin 624-10 with cooling mod.

Source: Rolls-Royce Production Drawing Office, February 1953.

[Bergerie1]

Megan, Thank you so much, I have sent you a PM.