mosquito single/ two stage merlin U/C was it the same ?

Because there’s not 300% reserve!

Land based aircraft are designed for 10 feet/sec (limit) landing and carrier based aircraft are designed for 14 feet/sec limit. When landing on ship, the runway maybe coming up at the same time your coming down

That makes sense. Cheers.

Because there’s not 300% reserve!

Land based aircraft are designed for 10 feet/sec (limit) landing and carrier based aircraft are designed for 14 feet/sec limit. When landing on ship, the runway maybe coming up at the same time your coming down

Therefore there was a 300% factor of safety in the design, which armourers could use to inform different load configurations. No need to change the U/C. The plane would fail to take off before the U/C would fail in practical terms.

Yet the Sea Mosquito had a different undercarriage. Why?

AP 970 ‘Design Requirements for Aeroplanes’ stipulated the design factors for aircraft accepted by the Air Ministry.
Chap Sect 9 (i) ” The U/C shock absorption capacity is to be such that the resultant ground reaction shall not exceed three times the weight of the aeroplane fully loaded when the aeroplane lands with the specified vertical velocity, thrust line horizontal”

Therefore there was a 300% factor of safety in the design, which armourers could use to inform different load configurations. No need to change the U/C. The plane would fail to take off before the U/C would fail in practical terms.

You need to read 970 very carefully as it says “not exceed 3 ‘and not “equals 3’ .

The U/C reaction factor is the ratio of the peak vertical load during a landing against the steady state 1g load at max take off weight. As such it sets the residual stroke (or shiny) that you see when the aircraft is weight on wheels. The U/C designer will set this value early in the design and it’s normally a lot less than 3. Typical values are 1.8 although I’ve seen values from 1.4 to 2.5. The value arrived at will depend on a good number of factors but, when finally calculated it must be below 3.

The one thing it’s not is a measure of reserve factor (or spare capacity) in the U/C.

Hi All,
thanks for the replies
jerry

Many thanks – would love to hear how it was done. None of the CG charts and tables I’ve seen for the Mossie offer any information on the matter…

I will ask

According to the legend / accepted wisdom, the beer was in modified wing tanks. Do you know if this is correct, or were more practical methods found?

TIA

Given that it is now nearly 70 years after the event I do not think that any secrecy statutes will now apply on this critical armament question !
I will ask him but as I think about it now he also took one or two passengers to and fro, implying that there was no navigator on what would have been a humdrum, repeat flight at a time when most twenty something pilots really wanted to be demobbed and somewhere else, so standards were slipping. Most of these passengers were soldiers with not enough leave time to catch a train to get back to the UK, so would cadge a ride back. Subject to fitting a keg through the access door I am sure there were many willing helpers to push a keg into the navigators seat ex UK.

It was an FB, so I figure the armourers would have put it in the bomb bay if they were doing it in a bulk, organised fashion, again I will ask.

A history of HM Customs I have read details the problems with handling contraband via postwar airforce flights to the continent, watches, stockings, gold etc. I am sure the stuff would be put anywhere, including in jettison tanks.

In the Pacific, there was a RAAF scandal centred around Clive ‘Killer’ Caldwell and planes filled with grog to be sold to US troops. Once things wound down and servicemen considered an uncertain future on ‘civvy’ street I am sure there was a tendency to think of ‘superannuation schemes’ to assist the transition. Contraband would fit wherever the human imagination might see that it would fit.

My father carried beer kegs from the UK and documents back from Nuremburg immediately post war in Mosquitos with no reported ill affects on the undercarriage, so beer kegs OK too.

According to the legend / accepted wisdom, the beer was in modified wing tanks. Do you know if this is correct, or were more practical methods found?

TIA

A very useful post. Just one comment however: the Mosquito was not originally designed as a PR aircraft but a bomber, with 2000lb internal stowage. I’m not aware of how much the initial design allowed for the fighter armament, but it was certainly considered from an early stage.

Yes

Hi
basically as per thread title,
curiosity mainly
the two stage merlin was slightly heavier
so was the undercarriage the same ?
tyres / pressures ?
U/C legs ?

likewise the initial bombload was 2000lb on the first mossies then some mod’d to 4000lb,
did the mod’d mossies have the same u/c ?

or did they all just sit lower on the ground when loaded.

I googled it & booked it, but I cant find anything about it, only info about the bombay mods.
cheers
Jerry

I don’t really know but I think the short answer is yes.

Based on the following :

Basic physics : Force = Mass X Acceleration, F= M X A

Therefore a standard Mosquito of a standard weight will transfer different forces to its undercarriage depending on the speed of landing, therefore the designer must allow for high speed landings that will stress the undercarriage to a certain level. So the undercarriage would be designed to cope with high speed emergency landings. This design factor could be adapted to the carrying of heavier loads, on condition that landings were more gentle. In practical terms very few aircraft would return with loads, and would land gingerly in any case.

In reflecting on the original Mosquito design, an unarmed reconaissance aircraft, later provided with machine guns, bombs and cannon of various calibre, let alone larger engines, there would appear to be a large design safety factor initially provided in the undercarriage, which allowed armourers to push the envelope with munitions. I have yet to see the steel components of the U/C different across Mosquitos. Only the wheels seemed to have changed, from single drum spoked wheels to dual drum wheels with greater braking capacity, consistent with stopping higher mass loads.

In respect of the U/C design, it was based on rubber buffers, in which APs allow a certain factor of compression to indicate whether they were sound or not. Since Malaya was occupied by the Japanese, cutting off supplies of rubber to the UK, and South American supplies were delayed in arriving through the US, a great deal of effort went into recycling rubber for military applications. Recycled crumb rubber was incorporated into new mouldings to an extent which has not been equalled to this day, with consequent affects on elastomer performance. Thus a practical response to heavier munitions loads was to ensure the purest rubber went into the most demanding applications, a simple way to extend the performance of the existing U/C design. Today, as you do in performance vehicles, you might use polyurethane instead of rubber for the same affect.

Some all up weights show that a 4,000lb bomb was well within design capabilities given other items were stripped out :

PR Mk XVI : 25,917 lb (unarmed)
B Mk XVI : 25,917 lb (no guns or cannon, 4,000lb bomb)
F Mk II : 19,670 lb (4 X 20mm cannon, 4 X .303 brownings)

AP 970 ‘Design Requirements for Aeroplanes’ stipulated the design factors for aircraft accepted by the Air Ministry.
Chap Sect 9 (i) ” The U/C shock absorption capacity is to be such that the resultant ground reaction shall not exceed three times the weight of the aeroplane fully loaded when the aeroplane lands with the specified vertical velocity, thrust line horizontal”

Therefore there was a 300% factor of safety in the design, which armourers could use to inform different load configurations. No need to change the U/C. The plane would fail to take off before the U/C would fail in practical terms.

My father carried beer kegs from the UK and documents back from Nuremburg immediately post war in Mosquitos with no reported ill affects on the undercarriage, so beer kegs OK too.