This is my first post, I've been trying to get to the bottom of this conundrum for some time, I am the person responsible for the model of WH793 on the link, my reasoning for the modified or should that be de modified wing tip is as follows.
This is the summery for the test flights carried out by WH793 in 1967 in the USA
SUMMARY
In a number of flights in the stratosphere over mountainous terrain in
the western U.S.A., much valuable data was collected. Flights "are planned
on the basis of tropospheric lee wave forecasts and were usually made along
wind at heights from the tropopause to about 50000 ft over California and
Nevada. Mountain waves, deduced from an analysis of the temperature along
the flight track, were moderate or strong on four flights. Moderate or severe
turbulence and marked temperature changes were encountered on three flights.
The results give an insight into the severity of the stratospheric environment
and the meteorological conditions in which the severe disturbances occur.
My reasoning behind the standard wing tips on 793?
The extended wing span would serve no advantage in a gusty turbulent environment, indeed it would only amplify any airframe buffet and add to crew discomfort.
The
PR.9 wing tip is not and was never intended to support any
weight, it is purely an increase in span. All the electrical wiring and fuel
goes to the same point as it dose on the standard
PR.7 wing and any other
Canberra wing. The wing on the production
PR.9's are basically that of the
B(I)8 but with the area increased. There would be no advantage in increasing the strength or re designing the tips on 793.
The wing tip of the Canberra is relatively easy to remove and the two types of wing tip and they are quite interchangeable.
I have closely studied photos of 793 from this time
and I can see no evidence of modifications to the tip tanks that would
indicate that they are fitted to anything other than the standard Canberra
wing tip. In order for the tanks to fit the
PR.9 wing the tip tanks need a
fairing to modify the shape to the new wing profile.
I wouldn’t fancy flying through CAT with two hefty pods hanging off a relatively flimsy structure. The small increase in altitude gained from the extra span wouldn’t warrant the extra work involved in all the cost and effort in redesigning and beefing up the
PR.9 wing tips, that for me is one of the biggest clues to the normal wing tips being re fitted, you wouldn’t go to all the trouble of ignoring a perfectly serviceable electrical connection and a designed attachment point for the tank/pod, to move them out to hang on a structure that was never designed for, or intended to carry anything other than a light. it can’t see it being for any radar related purpose either as I said before the SC.9 didn’t need to have it’s pods moved and other R&D Canberra’s flew with standard tip mounted pods. I just wish my WH793 PN’s had a three view and measurements!
John