The nightmare scenario is landing your Mosquito at the King Charles Coronation Airshow, having a wheel shatter and ground looping into the celebrity dias…when you do look at the cracks that have occurred, in every circumstance on these two wheels, the cast iron brake band remains unaffected, and the main substance of the wheel performing the function of supporting the aircraft remains in place. It is unlikely that the wheel will shatter into lots of pieces. What might occur is that the retaining ring comes apart, causing a tyre blowout. No doubt this is unpleasant, but the dias would probably be OK. I sense the wheel would have been telegraphing its unhappiness through micro cracks a while beforehand. These telltales could be compensated for/hidden by the brake drum and integrity of the rest of the wheel for quite some time.

I don’t think that replacing the original magnesium wheels with newly cast aluminium wheels is the answer. There is a lot of weight in the wheels and the aluminium wheels would be 30% heavier, requiring reworking of the hydraulics, centre of gravity and undercarriage design factors. I think that newly and properly cast magnesium wheels, subject to routine inspection and backed by a data logger, would be a sound method for keeping a Mosquito rolling over the next 100 years.

Visual inspection is worth doing

A set of original main wheels adopted for a hard life of postwar agricultural use was sent off to the sand blaster to clean up and have a closer look at cracks. To cut a long story short all cracks appeared in the weakest (least thick) part of the wheel casting AND these parts were visible from the outside. In other words simple visual inspection by a pilot or mechanic is a sound method of checking the condition of wheels. Under this logic, a crack is most likely to appear in the fluted section of wheel, which is readily visible. Upon further reflection, the fluted design acts to increase the surface area, which helps to dissipate braking heat. The thinner, fluted section will get hotter than the bulk of the wheel, so is also subject to more cycles of heat stress. Most of the landing stress is taken up by a steel T50 tube running through the wheel to the meaty spokes, connecting at either extremity to the rubber shock absorbing struts. The bead of the tyre is however retained on the rim, the weakest part, so the dynamic loads on the weakest part are coping with the dramatic spreading of the tyre upon landing and tendency to twist while turning. These particular wheels were used on an agricultural cultivator, so probably did hundreds of hours of constant work, twisting around corners at the end of the paddock. My only thought is to have a simple inertia logger on an aircraft, to track rough landings, peak loads and hours of use, linked to routine visual inspection.

The marks on the spokes are from fettling the original casting, made by Kelsey in Canada.

“The button on the starboard throttle lever was also a “P-T-T” button on some variants.”

Air Ministry, brilliant, that explains it. Even the string holding the power cable to the lever arm is the same ! Now I have a new question ! On the unarmed PR41 there is the standard stick top, which in an armed FB features an inset press button for the MG trigger. Do you have any information on what this press button may have been used for on a recon Mosquito? Camera control?

Ausflyboy,
Found another throttle box with complete bakelite to pattern off so that part sorted. Found an original drawing with complete labeling arrangements. That’s about as far as it’s got so far. Did discover the box case is cast magnesium, adding to all the other magnesium bits on the Mosquito, lots of magnesium.