Date:	Tuesday 1 August 2017
Time:	12:43
Type:	Rockwell Commander 114
Owner/operator:	Private
Registration:	G-TWIZ
MSN:	14375
Fatalities:	Fatalities: 0 / Occupants: 2
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Lydd (London Ashford) Airport, Romney Marsh, Kent -   United Kingdom
Phase:	Landing
Nature:	Private
Departure airport:	Lydd International Airport (LYX/EGMD)
Destination airport:	Lydd International Airport (LYX/EGMD)
Investigating agency:	AAIB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
AAIB investigation to Rockwell Commander 114, G-TWIZ: Damaged due to main landing gear collapse caused by upper side-brace failure, Lydd Airport, Kent, 1 August 2017. The incident was the subject of an AAIB Investigation, and the following is an excerpt from the AAIB Report

"The commander took off from Runway 21 at Lydd Airport, with one passenger on board. During the climb the commander moved the landing gear selector lever to up but he noted that the left MLG (Main Landing Gear) green light remained lit, indicating that this landing gear had not fully retracted. This situation was confirmed by Lydd Airport ATC by radio.

The commander recycled the landing gear several times, but on each occasion when the landing gear was selected up, the left mainwheel remained extended with the green light lit. When the landing gear was selected down, all three landing-gear green lights illuminated.

The commander decided to return to Lydd Airport and, on approach to Runway 21, ATC advised that all three landing gear legs looked down. The commander landed the aircraft normally, initially on all three wheels but as the aircraft slowed during the landing roll, the left MLG leg folded inwards. The commander turned the fuel selector and battery master switch to off before the aircraft stopped, and he guided the aircraft to the grass to the left of the runway.

Once the aircraft came to rest, the commander and his passenger exited the aircraft without difficulty. The aircraft sustained damage to the left wing and left cabin access step. During the recovery of the aircraft, it was discovered that the left MLG upper side-brace had fractured, preventing the left landing gear leg from retracting, or locking in the extended position

=AAIB Conclusion=
The aircraft’s left MLG leg collapsed during landing due to the fracture of the upper side-brace during retraction of the landing gear after takeoff. The upper side-brace fractured under the application of landing gear retraction loads due to the presence of a fatigue crack originating at a ‘cold shut’ casting defect. This casting defect was large enough to be detectable by radiographic (X-ray) inspection when the casting was manufactured and this inspection method was required according to the component’s classification under MIL-C-6021. This is the second occurrence of a Rockwell Commander 114 MLG collapse due to side-brace fracture originating at a casting defect within the side-brace.

=Safety action=
In response to this investigation the Type Certificate holder, Commander Aircraft Corporation, issued Service Bulletins SB-112-75 and SB-114-37, applicable to the Rockwell Commander 112 and 114 aircraft models
respectively. These Service Bulletins require inspection of the upper side-brace for cracking in the area of the retraction cylinder attachment and replacement of the upper side-brace if it is found to be cracked and not
repairable

=Damage Sustained to Airframe=
Per the above AAIB Report "Left landing gear upper side-brace fractured, damage to left wing and left cabin access step". The aircraft was repaired and returned to service, being sold on to its next (4th and current) owner on 8 June 2020

1. AAIB Report: https://assets.publishing.service.gov.uk/media/5aa7dfac40f0b66b625e2b0c/Rockwell_Commander_114_G-TWIZ_04-18.pdf
2. https://www.planelogger.com/Aircraft/Registration/G-TWIZ/
3. https://www.airport-data.com/aircraft/G-TWIZ.html
4. https://www.airport-data.com/aircraft/SE-GSP.html.
5. https://en.wikipedia.org/wiki/Lydd_Airport

This Rockwell Commander 114 was built in 1978, and was first registered in the United States as N5808N in March 1978 to the manufacturers, Rockwell International Copoaration. The aircraft was then sold to a new owner in Sweden, taking up the Swedish registration SE-GDP in February 1979.

The aircraft first took up a UK registration as G-TWIZ on 9 May 1990, passing through the hands of four owners between 9 May 1990 and 8 June 2020. Three of the four owners have been a Mr. Brian Cox, in partnership with a second co-owner (the re-registrations - on 9 May 1990, 11 August 1993 and 19 February 1999) were required to advise the CAA of the change of co-owner).

After the incident on 1 August 2017, the aircraft was repaired and returned to service, being sold on to its next (4th and current) owner on 8 June 2020. As at 25 May 2023, G-TWIZ has accumulated a total of 2,717 flying hours on the airframe

G-TWIZ Rockwell Commander 114 Lydd (London Ashford) Airport, Romney Marsh, Kent 9 September 2020

Date/time	Contributor	Updates
07-Jun-2024 06:27	Dr. John Smith	Added
07-Jun-2024 06:28	ASN	Updated [Accident report]