Date:	Monday 29 July 1946
Time:	day
Type:	North American Harvard T Mk IIb
Owner/operator:	ETPS RAF
Registration:	FS718
MSN:	14A-858
Fatalities:	Fatalities: 0 / Occupants: 2
Aircraft damage:	Destroyed
Location:	Millbrook station, Bedfordshire, England -   United Kingdom
Phase:	En route
Nature:	Military
Departure airport:	RAF Cranfield, Bedfordshire
Destination airport:	RAF Farnborough, Hampshire

Narrative:
Ex-USAAF 43-12559 (MSN 14A-858) Delivered to RAF as Harvard IIb FS718. To Aeroplane & Armament Experimental Establishment (A&AEE), Boscombe Down, Wiltshire. To Empire Test Pilots’ School (ETPS), Cranfield, Bedfordshire by/in January 1946.

Written off (destroyed) 29 July 1946. Bellylanded at Millbrook Station, Bedfordshire, after the throttle jammed and the engine lost power. Fire spread to airframe after landing, and aircraft burnt out.

The crew of two were students undertaking the No.5 course at the ETPS; during this particular sortie, the crew undertook aerobatic flying training. Having carried out and recovered from two intentional spins, the crew found that the throttle of Harvard FS718 had jammed.

The crew's reaction was to shut down the engine, as well as the fuel and ignition switches, prior to an attempt to force land the Harvard into a field in Bedfordshire. The Harvard caught fire immediately after landing at Millbrook, Bedfordshire, and was burnt out in the ensuing blaze. Both crew members survived

Crew of Harvard FS718:
Flight Lieutenant K E Walters RAF
Lieutenant R B Giblin USNR

The subsequent Board of Inquiry discovered that the throttle jamming was a well-known (and well-documented) side effect of the Stromberg carburettor of the type fitted to this aircraft. If the carburettor was tilted from the vertical (as happens during aerobatics) fuel spills from the float chambers, and exits through the main jets, either draining away or igniting harmlessly in the manifold chamber.

However, if the throttle is closed after such a fuel spill, as in the instance, the fuel ignites in the carburettor. In this incident, the butterfly plates in the fuel valves expanded and become jammed in the closed position, which made it impossible to move the throttle mechanism.

1. Halley, James (1999). Broken Wings – Post-War Royal Air Force Accidents. Tunbridge Wells: Air-Britain (Historians) Ltd. p.48. ISBN 0-85130-290-4.
2. Final Landings: A Summary of RAF Aircraft and Combat Losses 1946 to 1949 by Colin Cummings p.192
3. The Harvard File (John F Hamlin, Air Britain, 1988 p 90)
3. http://www.joebaugher.com/usaf_serials/1943_2.html
4. "RAF Write-offs 1946": Air Britain Aeromilitaria 1979 p.101: https://air-britain.com/pdfs/aeromilitaria/Aeromilitaria_1979.pdf
5. ETPS Cranfield ORB 1-1-1946 to 31-12-1949: National Archives (PRO Kew) File AIR29/1805: https://discovery.nationalarchives.gov.uk/details/r/C4101515
6. Photo of wreckage #1: http://ampthillimages.com/Media/Cranfield-Gall/pages/1946%20Plane%20Crash%2002.html
7. Photo of wreckage #2: http://www.ampthillimages.com/Media/Millbrook-Gall/pages/1946%20Plane%20Crash%2003.html
8. Photo of wreckage #3: http://ampthillimages.com/Media/RafCran-Gall/pages/1946%20Plane%20Crash%2004.html
9. Photo of wreckage #4: http://ampthillimages.com/Media/RafCran-Gall/pages/1946%20Plane%20Crash%2005.html
10. National Archives (PRO Kew) File AVIA 5/28/W2358: https://discovery.nationalarchives.gov.uk/details/r/C6578204
11. https://en.wikipedia.org/wiki/Empire_Test_Pilots%27_School#History
12. https://en.wikipedia.org/wiki/Cranfield_Airport#History
13. https://en.wikipedia.org/wiki/Millbrook,_Bedfordshire

Date/time	Contributor	Updates
23-Nov-2019 00:47	Dr. John Smith	Added
23-Nov-2019 00:48	Dr. John Smith	Updated [Narrative]
23-Nov-2019 00:48	Dr. John Smith	Updated [Narrative]
21-Feb-2020 14:13	Iwosh	Updated [Operator, Operator]
21-Feb-2020 14:29	Iwosh	Updated [Aircraft type, Operator, Narrative, Operator]
10-Apr-2020 20:02	Nick Slaughter	Updated [Operator, Operator]
04-Aug-2021 20:05	Anon.	Updated [Operator, Location, Operator]
14-Jun-2023 01:02	Dr. John Smith	Updated [[Operator, Location, Operator]]
15-Jun-2023 08:00	Nepa	Updated [[[Operator, Location, Operator]]]