Low-Tech

[Davaar]

On 19 April 1957 I last flew a Tiger Moth, G-AKCH. My recollection is that the ASI was basic, being:
(a) a fore-and-aft quadrant, gradated in knots, fixed to a starboard upper strut,
(b) to which was attached a spring-loaded hinged lever,
(c) at the lower end of which was mounted a lateral-axis plate,
(c) that was pushed back along the quadrant by the air pressure of movement,
thus indicating airspeed.

Old men forget, of course, and I wanted to check this. It was the work of moments to order a copy of the Tiger Moth pilot's notes from Amazon. That has duly arrived, but in an Australian version that indicates the cossetted treatment they got in Oz. No quadrants for them, we may be sure; right there on the instrument panel is a genuine ASI. That is no use to me.

Can anyone keep me right on the plate and quadrant?

[Mad (Flt) Scientist]

Not a Tiger Moth, but this web page (http://shortfinals.wordpress.com/tag/de-havilland/) has a picture of something very like you describe on a Leopard Moth.

All it consists of is a flat plate, with a few holes drilled in it, secured to a length of spring wire. As the air pressure builds up due to movement of the aircraft, the plate is forced backwards, giving a readout of the estimated speed on the graduated scale. There is even a red section, indicating when you are approaching the stall!

[henry crun]

Davaar: The two Tigers I flew at Shoreham a few years before your flight both had ASI's identical to the one you have described.

[Davaar]

Gentlemen, thank you. That illustration, Mad, is just as I remember it. Oddly enough the picture seems to show a swept-wing marque of the Leopard Moth, or one on which the wings have been folded for stowage.

In your heavy Tiger time, Henry, did you do any simulated IF? The Australian Pilot's Notes show a "blind flying hood", but of course that could be handled with the indoor, as it were, ASI. Not so easy if heavy canvas obstructs the view of the quadrant. And yet I remember pictures from long ago of exactly such hoods being used on UK Tigers in the War.

Any hints on how they did simulated IF? Of course if they did it with no view of airspeed at all, that probably just added extra poetry to "limited panel" and "If you can't take a joke you shouldn't have joined".

[henry crun]

Davaar: My Tiger flying was at aero club level for a PPL and the syllabus did not encompass simulated IF.

I have previously seen photos of the hood on a Tiger, but this is all I can find at present.
AWM Collection Record: 002154 - 1940-07-11. CONSTRUCTION OF TIGER MOTH PLANES AT DE HAVILLAND FACTORY - SYDNEY. HOOD FOR BLIND FLYING. TESTING THE HOOD ON A DUMMY ... (http://cas.awm.gov.au/photograph/002154)

[Davaar]

One keeps digging. Manifestly most pilots u/t cannot see through a canvas hood. Aha! What does Sherlock Holmes say?


It is an old maxim of mine that when you have excluded the impossible whatever remains, however improbable, must be the truth.
(The Sign of Four).

Well then. Since these chaps could not see through the canvas, and since I see no peep-hole in the canvas, they must have had an in-cockpit presentation, and here as so often Google does not fail. The TIGER MOTH AIRSPEED INDICATOR MKIXB of 1940 is graded from 0 - 160 “AIR M.P.H.”, and the Australian Pilot’s Notes show at the back a panel in different format that shows “AIRSPEED” (“Circa 1938"). From all this I infer that the early aviators did their simulated IF just as we all did it.

For the sheer joy of VFR, of course, the real pioneers swear by the old Quadrant Machmeter.