# Presentation: 477266

## Piston Design &Analysis

- 2-Stroke ROTAX Aircraft Engines

**ROTAX FLYING CLUB -  2001 ©**

## Piston Function

- Transfer energy to the crankshaft
- Control expansion under warm-up

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Measurements

- New pistons are measured at dimension “H”
- Used pistons are measured at widest point

**Piston Measurements**

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Analysis

- Compare piston to cylinder for clearance and evaluation of suitability of cylinder.

- Follow latest specifications from Rotax using only genuine ROTAX Aircraft engine parts.

**Piston Analysis**

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Design

- Pistons are neither cylindrical nor round.
- Pistons are made with special materials to control expansion.
- Piston rings have special functions and design.

**Piston Design**

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Failure Analysis

- 2-Stroke ROTAX Aircraft Engines

## Normal Pistons

- Deposits vary from oil ash, brown, tan, to black/brown.  Light color denotes higher cylinder temperatures.
- Light scoring is normal, varnish from blow-by gas is normal

- Copyright ROTAX FLYING CLUB 2001 (C)

## Heat Seizure

- Excessive heat, over 1200F/650C EGT
- Lean jetting or adjustments on carb
- Incorrect loading on propeller allowing excessive RPM

- Copyright ROTAX FLYING CLUB 2001 (C)

## Cold Seizure

- Thermo-imbalance of piston and cylinder
- Lack of warm-up
- Excessive temperature difference inlet to outlet on engine.

- Copyright ROTAX FLYING CLUB 2001 (C)

## Lack of Lubrication

- Excessive water ingestion causing loss of oil film on intake.
- Lack of intake air filter service.
- Results in excessive clearance

- Copyright ROTAX FLYING CLUB 2001 (C)

## Oil Failure/Oil Flash

- High temp in engine from cooling system failure, fan belt, coolant problems.
- Poor quality oils, auto, gear, unsuitable temperature stability.

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Scuffing

- Scuffing on exhaust side with no marks corresponding on intake.
- Thermal loading of oil film due to poor quality oil.

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Ring/Cylinder Scuffing	

- Oil breakdown due to:
- Improper break-in
- Poor quality oil
- Lack of oil in mixture
- Excessive loading of engine (propeller pitch)

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Dome Breakout

- Ignition timing failure, erratic firing.
- Lack of ignition damper, points engines.

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Dome Detonation

- Pre-ignition, leading into detonation
- Advanced ignition timing
- Spark plug heat range too high
- Low octane fuel

- Copyright ROTAX FLYING CLUB 2001 (C)

## Foreign Material 

- Material damage on piston from displaced or introduced object.
- Disassembly required of entire engine to find any additional material/damage and locate source.

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Scoring/Material Damage

- Objects between piston and wall.
- Complete disassembly required to find source and all related material

- Copyright ROTAX FLYING CLUB 2001 (C)

## Piston Fracture

- Complete disassembly required to remove all material
- Cause from excessive wear, excessive RPM with no load, excessive clearance fitting.

- Copyright ROTAX FLYING CLUB 2001 (C)