Date:	Tuesday 4 August 2020
Time:	16:20 LT
Type:	Hawker Sea Fury T.20
Owner/operator:	Norwegian Spitfire Foundation (operator)
Registration:	G-INVN
MSN:	41H-636070
Year of manufacture:	1951
Engine model:	Pratt & Whitney R2800-CB3 radial
Fatalities:	Fatalities: 0 / Occupants: 2
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Button End, Harston, Cambridgeshire, 7 miles NW of Duxford Airport -   United Kingdom
Phase:	Landing
Nature:	Private
Departure airport:	Duxford Airport (QFO/EGSU)
Destination airport:	Duxford Airport (QFO/EGSU)
Investigating agency:	AAIB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
AAIB investigation to Hawker Sea Fury T MK.20, G-INVN; Engine bearing failure and forced landing, Harston, Cambridgeshire, 4 August 2020. The AAIB Final Report was published on 16 September 2021, and the following is an excerpt from it:

"Hawker Sea Fury T.20 G-INVN had been undergoing an annual maintenance check for the previous nine months. Completion of the maintenance check had been delayed while a new engine oil cooler and tailwheel fork were manufactured. Engine ground runs were conducted during the week prior to the accident.

On the morning of the accident flight, the pilot flew the aircraft for a post-maintenance test flight. During his pre-flight checks he noticed the rudder trim had been rigged incorrectly and arranged for this to be rectified before the flight. He flew the aircraft for 15 minutes, completing several stalls, checking the trim and completing some general handling. He reported that the aircraft was "wonderful", the engine was "smooth" and there were no problems.

Weather conditions were good, with a light south-easterly breeze, CAVOK and temperature 22°C. A second flight was planned with a journalist, who had been invited to fly as a passenger in the Sea Fury. The journalist, who was also a qualified pilot, was writing an article about it.The flight was intended to last approximately 20 minutes.

The aircraft took off from Duxford for the second flight at 15:08 hrs and climbed to approximately 4,500 ft. As it climbed through 1,000 ft the pilot passed control to the passenger so he could experience flying it. As they had briefed, the pilot retained control of the throttle and rpm lever. They flew to the north conducting several turns, rolls, stalls and a loop.

Both the pilot and passenger reported that the aircraft was flying very well and they both recalled monitoring the engine instruments and seeing all parameters "in the green".

The first indication of a problem occurred as they were flying back towards Duxford, passing abeam Cambridge at 2,000 – 2,500 ft. The pilot noticed that the engine oil temperature was rising. He asked the passenger to check the gauge in the rear cockpit, and the passenger confirmed it was also showing the temperature rising. At this stage the temperature was still "in the white" (being above the green band but below the second red line). The pilot manually selected the oil cooler flap to open (by holding the switch to the open position for 12 - 15 seconds) and increased airspeed to increase the cooling airflow. Approximately 20 seconds later the oil temperature passed the upper red line and the oil pressure started to fluctuate.

At 16:18:25 hrs the pilot transmitted a MAYDAY call to Duxford. He considered diverting to Cambridge Airport, but discounted this because of a large built-up area in that direction. The passenger recalled that the engine was now starting to run rough, and he could smell oil and see oil on the windscreen. He looked over the side and could see smoke. The engine speed then increased beyond the 2,800 rpm takeoff limit, to 3,600 rpm.

The pilot brought the throttle and rpm levers fully back to contain the overspeed, reducing the rpm to 2,900 rpm. The pilot recalled the airspeed reducing but the engine was running fast, which felt counter-intuitive, and he remembered seeing brown smoke to his right. The engine and propeller then stopped rotating.

The pilot lowered the aircraft’s nose and found that it required an attitude of approximately 45° nose-down to maintain airspeed. He maintained 135 kt and remembered thinking "just keep it flying". The aircraft was descending rapidly, which he considered gave him limited options, and his view forward was restricted by oil on the windscreen. He selected a brown field slightly to the right and at 16:19:26 hrs transmitted a final call to Duxford: "just lost the engine, making a forced landing".

He kept the landing gear up as he believed this was the safest option for an off-airfield landing. He selected the flaps down, though unsure if there was enough hydraulic pressure for them to travel. He did not have time to select the fuel or magnetos off nor to open or jettison the canopy. The passenger did briefly consider jettisoning his canopy but thought he did not want to create extra drag.

Nearing the ground, the pilot flared the aircraft to reduce the rate of descent but did not hold it off. The aircraft hit the ground and bounced, then hit again and skidded across the field.

The aircraft slid into a tree on the far side of the field, which spun it around, and it came to rest in a hedgerow.
The pilot and passenger were able to climb out and move away from the aircraft. Local residents arrived quickly, and the pilot and passenger told them to stay away from the aircraft as there remained a risk of fire from the fuel on board. Another pilot who was flying nearby and heard the pilot’s transmissions was able to locate the wreckage and pass the location to Duxford. Emergency services from Duxford arrived shortly afterwards. The pilot and passenger were taken to hospital, both having suffered broken vertebrae.

=AAIB Conclusion=
The engine failure was caused by breakdown of the rear master rod bearing. The release of material and increased friction overwhelmed the oil cooling system and exceeded its capacity to maintain normal operating temperatures, resulting in catastrophic damage to the reciprocating components and eventually engine seizure. Symptoms of the bearing failure were visible before the accident flight, in the form of abnormal oil smoke, and might have been shown by a chip detector had one been fitted. However, from the moment excessive oil temperature was indicated, total engine failure could not be prevented.

The investigation did not discover precisely what initiated the bearing damage but determined that oil contamination was the most likely cause.

The pilot’s experience, including practice engine failures in a relevant simulator, assisted him in conducting a safe forced landing. Maintaining sufficient airspeed, whilst avoiding built-up areas and the temptation to reach an aerodrome, contributed to this outcome. The accident demonstrates the importance of an effective emergency briefing before flight, and the value of wearing appropriate head protection.

=Damage to airframe=
According to the AAIB report, the aircraft was damaged as follows: "Forward fuselage and wings detached from engine and tail section. Extensive internal engine damage".

1. AAIB Final Report: https://assets.publishing.service.gov.uk/media/612f8f04d3bf7f0387e8aa37/Hawker_Sea_Fury_T_Mk.20_G-INVN_10-21.pdf
2. https://www.cambridge-news.co.uk/news/cambridge-news/gallery/duxford-seafury-plane-crash-pictures-18716287
3. https://ukaviation.news/vintage-sea-fury-crashes-at-duxford/
4. https://www.itv.com/news/anglia/2020-08-04/two-injured-as-plane-crashes-near-duxford
5. https://cdn.jetphotos.com/full/6/98446_1571602942.jpg (photo)
6. https://www.bbc.co.uk/news/uk-england-cambridgeshire-53658215
7. Official history of aircraft: https://www.norwegianspitfire.com/sea-fury-t-20-g-invn-invincible/
8. https://www.huntspost.co.uk/news/sea-fury-aircraft-crashes-in-harston-1-6778016
9. https://en.wikipedia.org/wiki/Harston
10. https://www.openspotter.org/bild.php?blid=66174 (photo) .
11. https://aviation-safety.net/wikibase/156039
12. https://forums.flyer.co.uk/viewtopic.php?f=1&t=116320
13: Post crash interview with pilot: https://www.granthamjournal.co.uk/news/pilot-tells-of-miracle-130mph-crash-landing-in-vintage-fighter-plane-9119210/

Photo: AAIB

Forced landing or abandonment involves significant risk of injury in high performance aircraft. Operators and pilots can promote safe outcomes by providing clear safety briefings and ensuring all occupants wear effective head protection.
Read the reporthttps://t.co/i5VazSbUAk

— AAIB (@aaibgovuk) September 17, 2021

Before flying, taking the time to mentally rehearse the actions required in the event of an emergency will improve the chances of a safe outcome.

Read our report into a forced landing following an engine failure of a Hawker Sea Fury (G-INVN). https://t.co/i5VazStvrS

— AAIB (@aaibgovuk) September 16, 2021

During its second flight following maintenance a Hawker Sea Fury T MK.20 (G-INVN) made a forced landing following engine failure, near Button End, Cambridgeshire, 4th August 2020.
Read the report: https://t.co/EkV1UVhQP6 pic.twitter.com/GR8EIJHcsQ

— AAIB (@aaibgovuk) September 16, 2021

Date/time	Contributor	Updates
04-Aug-2020 18:06	RobertMB	Added
04-Aug-2020 18:50	harro	Updated [Embed code, Damage, Narrative, ]
05-Aug-2020 03:41	RobertMB	Updated [Operator, Embed code, ]
05-Aug-2020 08:52	A.J.Scholten	Updated [Source, ]
05-Aug-2020 12:52	Dr. John Smith	Updated [Time, Location, Source, Embed code, Narrative, ]
05-Aug-2020 12:54	Dr. John Smith	Updated [Source, Embed code, Narrative, ]
05-Aug-2020 13:04	RobertMB	Updated [Operator, Location, Narrative, ]
05-Aug-2020 13:58	Iceman 29	Updated [Embed code, ]
05-Aug-2020 15:28	borchi	Updated [Source, ]
07-Aug-2020 14:39	Dr. John Smith	Updated [Location, Source, ]
09-Aug-2020 09:17	sharla82	Updated [Source, ]
12-Aug-2020 16:20	Dr. John Smith	Updated [Source, Narrative, ]
16-Sep-2021 10:03	harro	Updated [Embed code, Narrative, Accident report, ]
16-Sep-2021 10:05	harro	Updated [Embed code, Photo, ]
16-Sep-2021 10:16	harro	Updated [Narrative, ]
27-Sep-2021 22:49	Dr. John Smith	Updated [Source, Embed code, Narrative, Category, ]
27-Sep-2021 22:50	Dr. John Smith	Updated [Embed code, Narrative, ]
27-Sep-2021 22:52	Dr. John Smith	Updated [Narrative, ]
27-Sep-2021 22:55	Dr. John Smith	Updated [Narrative, ]
27-Sep-2021 22:57	Dr. John Smith	Updated [Embed code, Narrative, ]