Slingsby Owners Club

The users knowledgebase for all things Slingsby T67

Slingsby Firefly T67M-Mk2

Picture of ex RAF Slingsby Fiefly

The T67M-Mk2 variant was the first of the series used by the Royal Air Force for Elementary Flying Training. It is a capable and efficient machine, but with a few limitations due to weight and balance. The aircraft is fitted with a Lycoming AEIO-320-D1B engine and a Hoffmann HO-V72L-V/180CB Propeller.

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Problems Encountered - Some with possible solutions
Symptom Solution
Oil Pressure gradually reads high while electric fuel pump is operating. (Full scale deflection >10bar) The oil pressure reading recovers to normal when the fuel pump is switched on and off several times.
The final solution to this was one of two possibilities. Firstly during the annual, the earthing connections from the engine were cleaned and re-seated. Secondly, the oil pressure sender was replaced with a new one.
Flap lever locking button will not come out while setting the flaps to the up position. According to the maintenance manual this will be due to the rigging of the flaps. However, independent engineers have found there is another cause.
If you have this issue it may be due to the engagement bar at the base of the flap lever fouling on the side wall. This requires the flap lever to be moved to one side or the other on its spindle using a spacer washer.
In need of replacement cockpit trim screws? At the time of writing (2010) Marshall-Slingsby have run out of spare cockpit trim screws (for which they charge £2.50+VAT each). These trim screws are a special order from a company in California (Stake Fastners) and the minimum order value is £100 for 200 units (and 4 week lead time). Should enough owners want spares, we can arrange for an order. Please contact the webmaster.
Throttle will not reduce below 1500RPM This may be due to the throttle cable sleve end detaching at the point at which the cable joins the solid rod end. Some aircraft have a temporary addition of some locking wire around the join holding the join together.
The only long term solution to this would be to replace the cable assembly. It is understood that this is a common occurance. Throttle cables are manufactured by a USA based company to the specific design, they can be sourced from Marshall-Slingsby.
Canopy lock - Key will not turn. This may be due to the plastic weather guard surrounding the lock openeing becoming distorted, thereby preventing the key from entering the lock fully. This is often due to the small retaining screws which hold the guard in place being slightly too tight.
This issue can be checked by removing the screws and plastic weather guard and trying the lock again. If the lock works, the problem is caused by the plastic guard.
Ensure the opening in the plastic weather guard is slightly larger than the key, all the way to the shoulder of the key. If not, a sharp knife could remove the excess inside the plastic weather guard slot.
Alternator Switch or Master Switch not functioning. This may be due to a small amount of grit which has found its way between the contacts. The cost of the replacement switch is approx £85 from Slingsby.
This may be solved on the Alternator switch by changing to use the redundant contacts on the other side of the switch.
Alternatively, using an air duster (designed for cleaning IT equipment) and blasting out any debris from the inside of the switch.
Military Yellow Colour The ex-RAF aircraft sporting the yellow and black colour scheme, may need touching up from time to time. The yellow colour specification is:
Golden Yellow colour spec BS381C/356, supplied by Courtalds the paint type is Gloss Polyurathane Pt No CA 40000.
Turners Trade Paints Ltd can supply the paint in aerosol format at £8 per can and £10 delivery.
It has been found that this paint tends to discolour at a different rate to the existing paint, so is now not recommended.
Parking Brake would not release on one wheel. This was believed to be a fault in the parking brake valve. The Cleveland 60-5 parking brake valve releases the pressure applied to the wheel cylinders by lifting two poppets inside the valve using a cam shaped bar. On this occasion the cam bar had been worn by the poppet lifting pins (cam follower) over time and was not lifting the poppet sufficiently. The solution found on this occasion was to replace the parking brake valve.
This problem returned a few months later, replacing the brake caliper solved the problem.
Transponder Conversion to Mode S. The ex-Babcock RAF elementary flying training specification aircraft are fitted with Bendix-King KT76A transponders. The direct repacement Trig TT31 Mode S transponder is as simple as its description, simply slide the KT76A out and slide the replacement Trig TT31 unit into its cage. The TT31 is not quite as easy to set codes on as the KT76 is, as the ENT button must be pressed ater each digit selection, however, the VFR function (to set 7000 quickly) easily offsets this limitation. The unit feels robust and the display is easily read in sunlight. The design complements the Bendix-King Silver Crown fit which exists in many T67s.
Altitude Encoder (Ex-JEFTS Aircraft fitted with Trans-Cal D120-P2-T)Picture of original transcal encoder Before replacing an existing Trans-cal D120-P2-T encoder it is worth reading the comments in the following thread.
Although the solid state unit would be a suitable option, it appears to require re-calibration every 2-3 years.
The tolerance on altitude encoders is +/- 125 feet. The D120-P2-T cannot be recalibrated in the field and must be returned to the factory.
Considering the price of the SSD120-30N is probably less than the cost to overhaul a D120-P2-T and they are pin for pin replacements, the SSD120-30N appears to be the most economical choice, as it is field adjustable.
Brakes binding on One possible cause of this is corrosion on the pistons in the calipers. This may be accelerated by operation on an airfield which has been treated with a de-icing fluid (often urea based).
The solution is to clean the corrosion off the piston side walls and apply a suitable grease.