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Mosquito Asymmetric Handling

Bit of a geeky question this one, but I have heard on the grapevine that the Mosquito had a very high Vmca compared to liftoff speed and that asymmetric handling was very difficult indeed.

Suggestion was that an EFATO below a certain speed was exceptionally difficult to handle and likely to end up in a Vmc departure and crash unless very well handled. Googling and searching on here hasn't uncovered any helpful information - can anyone point me in the right direction?

IIRC About 20 years ago the only flying example crashed at an airshow (Barton I think) with an engine failure during a climb below VMCA.

See Neil Williams' book "Airborne" for his description of flying what became Kermit Weeks' Mosquito and experiencing such an event at Booker (Wycombe Air Park). The valley adjacent to the aerodrome helped to save the day.

The Handling Notes say that Vmca (although they didn't call it that in those days of course) on a fully loaded Mossie was 200 mph (174kts). Lightly loaded and fitted with the narrow blade props it was a lot less but still pretty horrendous.

Neil Williams' problem at Booker isn't included in "Airborne", but it was published in Pilot - might be able to put my hands on a copy this evening.

Thanks for the replies - in the region of 160/170kts is a pretty scary number :eek: Is there a copy of the pilots notes available anywhere or do you know what typical unstick speeds were? Having had enough trouble learning to control an SE Taildragger on T/O and Landing I'd hate to try a beast like that OEI!

I have read the AAIB report into the loss of the Mosquito at Barton and though very illuminating regarding engine issues it has very little detail on the operational side of things.

You could try The Mosquito Page at:The de Havilland Mosquito Page

The Forum users (which includes some Mosquito aircrew and some absolute experts on the aircraft) either know or can find out most things about the Mosquito. They are also a cracking source of stories and a search on the site, or a query, might throw up all sorts of interesting tales about Mosquito assymetry.

Alternatively, in the 70s and 80s, Crecy published copies of the Pilot's Notes for several variants of the Mosquito and you might be able to find a copy somewhere.

Regards,

DS

I can't find my repro copy of the Pilot's Notes at the moment but I remember that safety speed, having once discussed it with an HS 748 pilot. I think the 748's is about 95 Kts!

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do you know what typical unstick speeds were?

If I remember correctly from three brief flights on the BMk35 fifty years ago, at max T/O weight lift off speed was around 120-125 knots, Vmca was 175 Knots IAS, but it took almost 50 seconds to get the gear up and accelerate through Vmc on a summer day. The only alternative was to reduce power on the live engine!

The very slow retraction time of the pneumatic gear retraction system was the big culprit; IIRC it had no pneumatic accumulator, or if it had one it was very small!

About five years ago there was an excellent article in Aeroplane magazine describing what is was like to fly and display RR299 - the last airworthy Mosquito. It was written by former BAe test pilot Peter Henley, and there is considerable detail about the slow undercarriage retraction etc. Although the brakes were pneumatic, the undercarriage was hydraulically operated, and even with both engines and hyd pumps working, the U/C took about 25 secs to retract. On one engine (and only one pump) this increased to about 45 seconds. The RAF Pilot's Notes state: "Although safety speed may be a little less in some cases, particularly at light loads and with narrow-blade propellers, it is recommended that a speed of 175kt be attained before starting to climb, especially if paddle blades are fitted". Mosquito RR299 did have paddle-blade propellers, and 100kt was a typical unstick speed. A long time to be at risk from the consequences of an engine failure after take-off.

The question the uninitiated would ask is "Why?"

Was it the sheer power of the good engine overcoming the rudder? High wing loading? Not enough fin or rudder area? Just not enough rudder authority? Cross section area of the dead side? Drag from the dead prop? Was the prop on a dead engine featherable?

One would have thought that a Merlin on full throttle would have little problem overcoming even the drag of undercarriage in such a low drag aircraft

Interesting comparison with the pictures I have seen of a shackleton flying two dead engines on the same side (for display) apparently quite manageably.

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Was the prop on a dead engine featherable?

Yes it was. Peter Henley described it thus:-

"The tasks facing the pilot were daunting. Drag reduction was paramount, so the undercarriage and flaps had to be retracted as soon as possible, while flying the aeroplane with the left hand, because undercarriage and flap levers were in the centre of the instrument panel. Drag from the windmilling propeller of the failed engine would have been very high, so manual feathering would have to be carried out dextrously while flying, first with the right hand and retracting the relevant throttle and pitch levers (to the left of the pilot's left thigh), then changing hands to free the right hand to reach the feathering buttons, which were in front of the right-hand seat".

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a shackleton flying two dead engines on the same side (for display) apparently quite manageably

That's a case of good energy management - feathering two engines of a four engined aircraft at relatively high speed (i.e. well above Vmca) is a very different thing than feathering an engine from below Vmca, while trying to accelerate to it.

While operating below Vmca the control issue is of primary importance, drag being a secondary challenge if control can be maintained. By definition it cannot, of course, without reducing power or increasing speed.

I found the Neil Williams article about his Mosquito Moment at Booker - also includes a fraught few minutes in Philip Mann's Yak 11!

If anyone would like to see a PDF copy, PM me your email address.

The following comes from the Pilot Notes for the Mosquito FB6.

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40. Take-off
(i) Carry out items (95) to (105) in the Pilot's Check List.
(ii) Taxy forward a few yards to straighten the tailwheel.
(iii) Open the throttles slowly, checking any tendency to swing by coarse use of the rudder and by differential throttle movement. There is little tendency to swing if the engines are kept synchronised.
The travel of the throttle levers is very short for the power obtained.
Coarse use of the throttles will aggravate any tendency to swing.
(iv) When comfortably airborne, brake the wheels and raise the undercarriage, check that the undercarriage locks up; if it does not hold the selector lever up for five seconds.
(v) Safety speed at a weight of approximately 17,000 lb. flaps up or 15° down at +9 lb./sq. in. boost is 155 knots. At + 18 lb./sq. in. boost it is 170 knots. These speeds however, may vary considerably with individual aircraft.
(vi) Before raising the flaps, if used, trim the aircraft slightly tail heavy.

55. Engine failure during take-off
(i) The handling characteristics of individual aircraft differ considerably according to age and load. Except in cases where it is known to be less ; at approximately 17,000 lb., safety speed should be assumed to be 155 knots at + 9 lb./sq. in. boost and, if the engines have not been de-rated 170 knots at + 18 lb./sq. in. boost.
(ii) If safety speed has been attained, the aircraft will climb away on one engine at climbing power at about 135-140 knots provided that:—
(a) The propeller of the failed engine is feathered and the radiator shutter closed.
(b) The flaps are fully up.
(iii) The drag of a windmilling propeller is very high and unless feathering action is taken immediately, control can only be maintained at the expense of a rapid loss in height.
(iv) The aircraft accelerates slowly to the safety speed at + 18 lb./sq. in. boost. If high power is used for take-off, it is recommended that climbing power is used as soon after take-off as is possible.

57. Single-engine landing
(i) While manoeuvring with the flaps and undercarriage up, a speed of 140-150 knots should be maintained ;
(ii) A normal circuit can safely be made irrespective of which engine has failed. The checks before landing should be carried out as for a normal landing, but it should be remembered that the undercarriage will take longer to lower on one engine—approximately 30 seconds at 2,850 r.p.m. —and, owing to its high drag, height will be lost once it has started to lower.
(iii) When across wind, flaps may be lowered 15° and the live engine used carefully to regulate the rate of descent. Speed should not be allowed to fall below 135 knots until it is clear that the airfield is within easy reach ; flaps may then be lowered further as required and power and speed reduced as height is lost, aiming to cross the airfield boundary at the speeds quoted for an engine assisted landing.

58. Going round again on one engine
Going round again is only possible if the decision is made while ample height remains and before more than 15° of flap is lowered. The height is required in order to maintain the speed above the critical speed, for the high power necessary, while the undercarriage and flaps are retracting. When the decision to go round again has been made:—
(i) Ensure that the speed is not less than 135 knots, and then increase power on the live engine to +9 lb./sq. in. boost and 2,850 r.p.m.
(ii) Raise the undercarriage.
(iii) Increase speed to 140-150 knots.
(iv) Raise the flaps and re-trim.
(v) If the engines are not de-rated, power higher than +9 lb./sq. in. should only be applied carefully and within the limits of rudder control.

Handling
The controls are light and effective and manoeuvrability is good. The rudder should not be used violently at high speeds. When two-tier R.P. or rails are carried, aileron control is poor at low speeds, i.e., during take-off and approach to land.

By way of comparison, the take off safety speed for the Beaufighter (Merlin engines) was 139 knots, and for the P-38 113 knots. A little disparity arises when comparing figures as the Beaufighter is at take off power whereas the P-38 advises to reduce power on the good engine to contain the yaw. Excessive yaw will result in stalling of the vertical tail surfaces and the rudder forces reverse. The power on the good engine will then have to be materially reduced, and considerable rudder force will be necessary to regain control.

Read Colin Cummings excellent books on RAF aircraft accidents to gain some idea of the Mossie's horrendous record.Not something we realised in those postwar years.

.....perspective is everything.

Experienced Mosquito pilots are getting very thin on the ground now. I knew a few, and they always spoke of the a/c in very, very glowing terms. Sure, if you look at the figures - especially the blue-line speed, and compare it with more modern, more benign machines, it might look a bit scary. In truth, many, if not most wartime a/c would feel a bit scary to modern pilots, especially when bombed-up and full of fuel....and in the dark... The records show that the Mosquito had a vastly lower rate of loss than the Lanc' for example. It was not unusual for damaged a/c to fly home all the way from Germany on one engine, - and never drop below 200mph to boot. They also flew home with heavy damage.
I have an excellent wartime book, 'Low Attack' by W.Cdr Wooldridge. I think they were 105Sq. and based at Marham from memory. They'd been using the Blemheim previously and were glowing in their praise of the Mossie. It was light years ahead.
Unlike many modern 'warbird' pilots, wartime crews flew these a/c all the time and often at night. They knew the limitations of the a/c very well and acted accordingly. Sure there were accidents (Tony Ben's brother was killed in an EFATO in a Mossie for example.). At least the Mossie would fly on one engine and even accelerate and climb if correctly handled. Many other types of that period were very vulnerable to an EFATO and were only going one way after an engine failure ..... DOWN. Many heavily-laden bombers crashed on t/o, especially at night.
For around three years there wasn't anything in enemy hands that could catch it. The PR versions roamed the length and breadth of Axis-held Europe with virtual impunity at up to twice the altitude of most a/c. The Mossie could carry the same load as a B17, faster, higher and further, for vastly less casualties, less fuel, less materials, less manpower to produce etc....oh, and they were churning them out from furniture factories. It was also the original 'MRCA', and filled every role and flew in every theatre - a truly amazing record.
The Mossie was a military a/c, mostly flown under combat conditions. Any narrow discussion of one very narrow aspect can give a very false and distorted impression to what was, arguably, the finest a/c of the war. As an a/c to go to WAR in, it was absolutely in a league of it's own....

GQ2
I have never doubted that and, as you say, a discussion of a narrow quality of an aircraft without context is somewhat unhelpful, however I was just curious as to the compromises made to get such a fine war instrument.

There were other planes that were good for purpose but otherwise "difficult" for instance the Typhoon. The compromises, flying qualities and constuctipon/engines are an endless fascination.

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they always spoke of the a/c in very, very glowing terms

Well said, GQ2, you're absolutely right.

The thing I remember most clearly from my very brief exposure to the Mossie 50 years ago was the utterly exquisite harmonisation of the flight controls. Until experienced it is very difficult to define control harmonisation, yet it is probably the single most important contribution, after meeting the regulatory requirements, that a test pilot can make to the satisfactory developoment of an aircraft's handling characteristics.

Mosquito control force gradients in all three axes could not be more perfect and was the standard against which all aircraft I subsequently flew were judged. Geoffrey deHavilland and John Cunningham certainly got it right that time!