Date:	Tuesday 13 June 1950
Time:	day
Type:	Cierva W.11 Airhorse
Owner/operator:	Cierva Autogiro Company
Registration:	VZ724
MSN:	W.11/1
Fatalities:	Fatalities: 3 / Occupants: 3
Aircraft damage:	Destroyed
Location:	Pragnell’s Farm Eastleigh, Hampshire -   United Kingdom
Phase:	Take off
Nature:	Test
Departure airport:	Eastleigh Airport, Southampton (SOU/EGHI)
Destination airport:
Confidence Rating:	Information is only available from news, social media or unofficial sources

Narrative:
The Cierva Air Horse was, when it was built, the largest helicopter in the world and one of the few helicopters to have three rotors. It was designed by the Cierva Autogiro Company (which evolved out of the Scottish helicopter company, G & J Weir). The Air Ministry ordered two Air Horses under Air Ministry Specification E.19/46 and in 1946 Cierva subcontracted their construction to Cunliffe Owen Aircraft at Eastleigh. However, the company failed in 1947 and filed for bankruptcy. It's not clear whether, by then, Cunliffe Owen had completed both or either of the Air Horses or, if not, where and by whom they were completed.

The two Air Horses were registered G-ALCV and G-ALCW, but seem to have flown principally bearing the military serials VZ724 and WA555. The first of the two was completed in 1948. It was a static exhibit at that year's SBAC show at Farnborough in early September 1948. It was first flown by Alan Marsh (Cierva's chief test pilot) at Eastleigh on 7 December 1948 as VZ724. It did so with an all up weight of 14,000 lbs, a world record for a helicopter at that time. At the following year's Farnborough (September 1949) show it featured in the flying display.

Test flying of VZ724 continued until 13 June 1950, when the Air Horse crashed at Eastleigh due to fatigue failure of the swashplate carrier driving link of the front rotor hub. It is claimed that the part was inadequately machined. This failure caused the collective rotor pitch to increase to maximum, causing the aircraft to pitch up and then nose down, resulting in it diving into the ground. However another source claims that the hub failure caused the front rotor to make contact with one of the rear rotors, leading to the disintegration of the two and the inevitable uncontrolled fall to earth. There were three fatalities - Alan Marsh, John "Jeep" Cable (the Ministry of Supply test pilot) and Joseph Unsworth (the flight engineer). At the inquest into their deaths, held at Eastleigh on 29 July 1950, verdicts of death by misadventure were returned.

As a design, the Air Horse was ahead of its time and is said to have been more complicated than the technical know-how of the time could comprehend. It is also said, by those with knowledge of it, that vibration was a real issue (all three rotors were powered by a single Merlin engine, within the fuselage of the helicopter, with power to the three hubs being via a gearbox and, it seems, shafts).

After the crash of VZ724 Cierva lost interest in the project and transferred the development work to Saunders Roe. But not long thereafter the Air Ministry/Ministry of Supply withdrew funding and development ground to a halt. The second Air Horse (WA555/G-ALCW) was then put into storage by the Ministry of Supply at a deport at Byley in Cheshire, before it was scrapped by Staravia in February 1958 (some say 1960). Maybe if the issues which caused VZ724 to crash had been understood and resolved, the Air Horse might have had a future.

According to the Air Ministry aircraft record card the first Air Horse was first registered (C of A 12431/1) on 11 August 1948 to The Ministry of Supply, Millbank, London W1. The registration G-ALCV was cancelled on 7 July 1950 as "crashed" (presumably a reference to the above crash on 13 June 1950).

1. National Archives (PRO Kew) File AVIA 6/16897: https://discovery.nationalarchives.gov.uk/details/r/C4027218
2. National Archives (PRO Kew) File DSIR 23/19265: https://discovery.nationalarchives.gov.uk/details/r/C2433482
3. https://trove.nla.gov.au/newspaper/article/2784183
4. http://www.caa.co.uk/docs/HistoricalMaterial/G-ALCV.pdf
5. https://www.flightglobal.com/pdfarchive/view/1950/1950
6. https://www.flightglobal.com/pdfarchive/view/1948/1948
7. http://sussexhistoryforum.co.uk/index.php?topic=7659.0
8. https://cwsprduksumbraco.blob.core.windows.net/g-info/HistoricalLedger/G-ALCV.pdf
9. https://en.wikipedia.org/wiki/Cierva_Air_Horse#Operational_history
10. G-ALCV at Farnborough in September 1948: https://www.flickr.com/photos/dwhitworth/5518360086
11. https://www.helis.com/database/cn/42127/
12. http://www.hampshireairfields.co.uk/ah1900/cicuprod.html
13. http://www.aviationbanter.com/attachment.php?attachmentid=94582&d=1503065277
14. http://www.ukserials.com/results.php?serial=VZ
15. http://www.hampshireairfields.co.uk/hancrash.html
16. National Archives (PRO Kew) File AVIA 54/85: https://discovery.nationalarchives.gov.uk/details/r/C3114243
17. National Archives (PRO Kew) File AVIA 54/86: https://discovery.nationalarchives.gov.uk/details/r/C3114244
18. National Archives (PRO Kew) File AVIA 54/87: https://discovery.nationalarchives.gov.uk/details/r/C3114245
19. National Archives (PRO Kew) File WO 32/18897: https://discovery.nationalarchives.gov.uk/details/r/C2552042 .

First prototype Cierva W.11 Airhorse G-ALCV on display at Farnborough in September 1948:

Date/time	Contributor	Updates
09-Apr-2013 12:43	TB	Added
29-Apr-2013 17:18	Dr. John Smith	Updated [Date, Aircraft type, Registration, Cn, Operator, Location, Phase, Nature, Departure airport, Source, Embed code, Narrative]
05-May-2013 13:28	Dr. John Smith	Updated [Narrative]
30-Sep-2014 16:55	TB	Updated [Operator, Location, Source, Embed code, Narrative]
21-Feb-2020 03:18	Dr. John Smith	Updated [Time, Location, Source, Embed code, Narrative]
26-Dec-2020 16:24	Dr. John Smith	Updated [Registration, Source, Narrative]
26-Dec-2020 16:28	Dr. John Smith	Updated [Source, Narrative]