Bing 54 carburator update, Bing 54 carburator needle
and clip update.
|Bing 54 carburator needle and
All ultralight aircraft using the Bing 54 carburator used on Rotax and
Hirth aircraft engines.
AAIB Bulletin No: 12/98 Ref: EW/G98/07/25 Category: 1.4
Aircraft Type and Registration:
Rans S6-ESD XL, G-MZBD
No & Type of Engines:
1 Rotax 503 piston engine
Year of Manufacture:
Date & Time (UTC):
19 July 1998 at 1700 hrs
Sittles Field, Nr Lichfield, Staffordshire
Type of Flight:
Persons on Board:
Crew - 1 - Passengers - 1
Crew - None - Passengers - None
Nature of Damage:
Significant damage to the landing gear and cockpit floor
Private Pilot's Licence
Commander's Flying Experience:
226 hours (of which 25 were on type)
Last 90 days - 32 hours
Last 28 days - 20 hours
Aircraft Accident Report Form submitted by the pilot telephone
enquiries with owner, aircraft repairer and other agencies.
The pilot reported that during the final leg of a cross-country
whilst flying at approximately 1000 feet amsl, the engine RPM
from 5,800 to approximately 3,800 and the unit began to run very
Various throttle positions were tried, none of which improved the
situation. After some 30 seconds the engine stopped completely, the
by then being 750 feet agl or less.
In view of this low height, no attempt was made to re-start the
The pilot judged that the only safe landing field available was
beneath the aircraft and accordingly he commenced a steep right-hand
through 360 degrees to position the aircraft into wind and facing up
local slope. Unfortunately, after straightening out the aircraft,
insufficient airspeed and height remained to enable the aircraft to
round-out into the uphill flight-path necessary for a landing. The
aircraft stalled whilst about 10 feet agl.
Examination of the engine subsequently revealed that a needle in the
of one of the carburettors had detached and fallen into the jet area.
detached as a result of breaking in the plane of the locating groove
severe machining type wear had been inflicted as a result of
rotation of the needle relative to its mounting circlip. This problem
been encountered in the past; it occurs under certain conditions of
vibration and resonance. It led to the fatal accident of the similarly
powered Colb Twin-Star, G-MWWF, in 1994, see AAIB Bulletin 11/94. As a
result of that accident, the AAIB made the following comments and
recommendation to the CAA:-
"The cause of the partial engine failure was that the needle on
carburettor had worn through at the circlip and had dropped into the
carburettor jet, restricting the flow of fuel to the rear cylinder.
needle was retained in position by a circlip which was spilt at the
of the hole holding the needle; the edges of the split had 'machined'
the groove in the needle as it rotated under the forces generated by
vibration. This problem is well known and both the UK distributor and
manufacturer (Rotax) have issued safety bulletins calling for a 50
inspection of the needle and an ultimate life of 150 hours.
Rotax are developing a modification for new production which will
introduce an 'O' ring to each side of the circlip to prevent the
rotating. The modification is due on the production line at the end of
year. It is therefore recommended that:-
94-35 The CAA require that the modification to the carburettor needle
fixture on Rotax engines be made retrospective and mandatory, and that
the meantime the 50 hour check be also made mandatory."
The CAA did not accept this recommendation. Their reasons were stated
their document 'Follow-Up Action On Occurrence Report ' No F30/94.
The modification ultimately engineered by the manufacturer is slightly
different from that described above. It has now been available (at
cost) for retrospective installation for approximately 18 months. It
installed on current production engines, although the fact that
and builders of kits frequently store engines for extensive periods
results in new aircraft continuing to come into use with engines which
have been built before the modification became part of the production
The aircraft involved in this accident is understood to have completed
hours total flying at the time of the accident.
This update prevents wear on the
needle and clip. The update requires the purchase of part #831-715 a rubber 0 ring which
fits on to the top of the needle, and the installation of a NEW style retaining cup part #
827-347. The new retaining cup has a cut out for the rubber O ring which puts pressure
down on the clip and needle to prevent them from turning and wearing.
|New style retaining cup part # 827 347 - $15.95
|New O ring which can be installed
on older style needles
part # 950 430 - $3.95
|New style clip part # 963 500 - $8.75
Updated needle, clip, O ring and cup
This is the new style of clip which can be used
with the new rubber 0 ring and retaining cup.
Click here for a quick way to
check your needle and clip!
Click here for Rotax update in pdf format
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