Denney K Tfox Mk 2, G-BWHV No & Type of Engines: Rotax

AAIB Bulletin: 3/2007 G-BWHV EW/G2006/07/28 ACCIDENT Aircraft Type and Registration: Denney Ktfox Mk 2, G-BWHV No & Type of Engines: Rotax VL 582 pston engne Year of Manufacture: 997 Date & Time (UTC): 8 July 2006 at 22 hrs Location: Treforest Industral Estate, Pontyprdd Type of Flight: Prvate Persons on Board: Crew - Passengers - Injuries: Crew - Passengers - Nature of Damage: Arcraft destroyed Commander’s Licence: Natonal Prvate Plot’s Lcence Commander’s Age: 53 years Commander’s Flying Experience: 24 hours (of whch 110 were on type) Last 90 days - 3 hours Last 28 days - 3 hours Information Source: Arcraft Accdent Report Form submtted by the plot Synopsis The arcraft suffered a substantal loss of engne power Turnng back for the return nto Cardff, the plot and crashed nto an ndustral estate followng an retuned the rado for the Cardff ATIS and was makng attempted forced landing into school playing fields. a turn to the left when he and hs passenger heard loud screechng sounds, and bangs, from the engne. The History of the flight plot throttled back and checked the engne nstruments, The plot and passenger, hs wfe, had planned a whch were normal. He found that the engne would local flight and took off from Cardiff Airport at about run at about 4,000 rpm - he commented that, normally 1145 hrs (UTC), departng to the north. Crossng 5,000 to 5,500 rpm was needed to mantan heght, wth the M4 motorway, clear of controlled arspace, they dle at about 3,000 rpm, so the arcraft was descendng descended to ,000 feet for a tmed clmb to 2,000 feet, at ths pont. ther assgned heght. The tmed clmb was satsfactory and the plot turned up the Rhonda Valley towards The pilot looked for landing fields but could see nothing Pontypridd for local flying. sutable n the upper valley. He decded that he could not clear the valley, towards Cardff, so he selected the Hawthawn playing-fields, near the Treforest Industrial © Crown copyrght 2007 45 AAIB Bulletin: 3/2007 G-BWHV EW/G2006/07/28 Estate, as hs only landng ste. He set up for an mass, enclosed wthn a cylndrcal body, movng n a approach over the open end of the playing-fields but, at viscous fluid to provide rotary vibration damping. the ‘threshold’ found himself still 2 to 3 metres high and much too fast. He managed to put the wheels on the The engne from G-BWHV was later examned at an grass twce but bounced each tme and, assessng that overhaul agency. The major failure identified within the row of trees at the far end of the field was too close, the engne, before ts mpact wth the ground, was n opened the throttle. the hydrodamper, where the small outer flange of the cylndrcal body had separated, resultng n the loss of The arcraft cleared the trees and the plot was turnng the viscous fluid. It was not clear what mechanism had to the left, for another attempt into the same field, when caused the subsequent loss of power but the engneer the engne cut completely. The arcraft descended examnng the engne consdered t possbly due to towards ndustral buldngs and the left landng gear contamination from the fluid released from the damper. leg struck a roof, spnnng the arcraft around so that t Examnaton of the fracture surface by a metallurgst fell next to the buldng t ht, choppng off the tal on ndcated the falure had been through a fatgue a brck wall. mechansm, startng wth fatgue orgn ponts on the inner surface of the flange. The crew compartment came to rest nverted on the A4054 road and the plot told hs wfe to wat for The engine manufacturer was consulted on this flange hm to help get her out. He released hs harness and falure and commented that they had not seen any crawled out of the rear of the compartment, to reach smlar cases. the passenger sde of the arcraft. Meanwhle hs wfe Analysis had released her harness and the plot was able to help her out. Together they reached the grass at the sde of The plot consdered that the falure to make a the road and became aware of people comng to assst. satisfactory forced landing at the first attempt was at There was no fire and the passenger and pilot were least partly due to a lack of recent practce of glde taken to hosptal, although they assessed ther njures approaches to an actual landng: hs most recent as minor. Both seats were equipped with full ‘four- practce to a completed landng had been n September pont’ harnesses. 2005, although he had done a practce, to 500 feet, the prevous day. He assessed that, n the approach Examination to the playing fields, he should have gone further The Rotax 582 s a two-cylnder two-stroke engne downwnd but was ntmdated both by the state of the drvng the propeller, n ths nstallaton, through a engne and the presence of the ndustral buldngs. He smple reducton gearbox. In the case of G-BWHV, the also consdered that, to reduce energy on approach, a engine was later modified with a factory-provided rotary sdeslp would have helped but that he dd not realse hydrodamper unt, to reduce the level of vbraton. The he was too hgh and fast untl t was too late. desgn of ths damper s conventonal, wth a torodal © Crown copyrght 2007 46.

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