Approvals ….

Got an email from the busy LAA this morning … working on a Saturday … so good to get feedback.

Having never submitted an aircraft modification before I am still learning the sequence and paperwork that is required.

The 12 pages of what is called a MOD3 went through quite a lot of iterations but, even though we have now reached a high degree of acceptance I have omitted to provide some other elements:

  • A completed worksheet – basically setting out the key elements
  • An updated section for inserting in the Pilot Operating Handbook POH
  • A PMR – Permit Maintenance Release

Spent this evening completing these so just need to meet up with my local LAA engineer for counter signature ..

Update to POH

POH Addendum Smoke System
Smoke System – Principle of Operation
The oil smoke tank uses a kit supplied by American supplier Smokin Airplanes and comprises the following elements:
– Smoke oil tank with associated pump
– Feed pipes and delivery pipes
– Spray bar fittings for exhaust pipes
– Electrical switches and fuses

The tank accepts a paraffin based oil (Baby oil) and the electrical switch , momentary switch provides power to the pump which draws oil from the tank into aircraft grade aeroquip rubber hosing.
The hosing routes to the rear of the stainless bulkhead and passes into a T bar aeroquip fitting that splits the single feed into a steel braided double feed that connects to spray bar atomiser injectors fitted into each exhaust outlet.

Fitting Of Oil Tank
The oil tank is fitted into the front seat (P2) location. The seat base and seat back are removed prior to installing. This leaves the Sherwood standard plywood seat base which has had 2 holes drilled in to accept 2 alloy pins on the underside of a tailor made ally mounting tray.
The mounting tray has lips on all sides to ensure the oil tank does not move in any direction.
Underneath the plywood seat base 2 alloy brackets have been riveted in position on the outer edge of the 2 longitudinal seat rails. These brackets accept a 1” wide ratchet strap.

Weight and Balance Consideration
As the oil tank is located in the P2 position, and this location is dead centre on the C of G , mainspar there is no change to weight and balance whether the oil tank is empty or full.

Filling the Tank
The tank is generally filled outside the aircraft but it can be filled in situ with a suitable long stemmed filler flex pipe. Filling is through a large hole in the top of the tank which has a securing screw cap. Do not overfill the tank .. 3/4 is sufficient for approx 4 mins of continuous smoke.

There is an overflow pipe if excess washes over in any steep turns. This pipe routes to the underside of the aircraft behind the u/c.
A quick release break valve is fitted to prevent spillage. The tank can be removed , even if oil remains in the tank.

Smoke Operation
The smoke can be operated once the engine reaches suitable temperature. Usually 150’ and above EGT.

There are 3 ways of operating the smoke:
– The main switch panel has a 3 position switch, continuous on, Off and Armed for intermittent
– A remote Push button allows momentary operation of smoke .. IF the primary switch is in the UP (Momentry) position
– If the primary switch is set to ON, the. The pump operates until it is turned off.

Note .. a red light is illuminated all the time the pump is in operation
Note .. the pump will continue to operate even if no oil is in the tank amd the switch is in the ON position.

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