Leak Check (Air, Hydraulic, Oil, And Fuel)

[AeroTech]

Hi,

If I am not mistaken dry motoring drives N2/N3 to around 20%-25% N2/N3. I am assuming N1 will be driven at very low speed: may be 1% or 3% N1 ???

a) When performing leak check using dry motoring, the thrust reversers cowls or ducts are open. So based in your experience & A.M.M and if you are close to the core engine checking for leak, does the leak check represent a safety issue because the fan is sucking air through the core engine (T/R cowls open) especially for high or medium bypass engine?

b) Based on your experience & A.M.M, is dry motoring efficient to detect specific leak check: air, hydraulic, oil, or fuel ? I am asking this question because there is leak check using idle thrust or part power thrust. How often (approximate percentage) dry motoring leak check is efficient versus idle thrust or part power thrust leak check ?

c) How often (approximate percentage) leak checks (the 3 types of leak checks) are used in gate (line maintenance) or hangar ?
Does the leak check affects the turn-around time of the aircraft ?

Feedback appreciated.
Regards.

[TURIN]

a, No, unless you climb in to the intake and stick your hand in the blades. :uhoh:

b, Depends where the leak is. A fuel leak in the HP section of the engine fuel system will need a wet motor or an engine run (dry powder leak detectors can help). A hydraulic leak may show up, an oil leak may need higher power to get the pressure up. A duct leak from an engine bleed manifold would be tricky with a dry motoring.

c, In today's line environment with turnround times on a wide body twin typically 80 mins, any unscheduled maintenance that means you have to get the cowlings open will probably mean a delay.

[itsresidualmate]

As Turin mentioned, quite common to use the dye penetrant 'developer' white powder. Spray it around the suspect couplings, close cowls, run, re-open, see if any evidence of leaks where the dry powder is.

[spannersatcx]

We used to use silver foil (not the one from the supermarket) on the bleed ducts of the CF6-50 on the 747. Just one of several ways of finding bleed leaks.
The AMM tells you what test you need to carry out after changing certain components, which could be dry/wet cycle, idle or high power EGR's. Dry motoring can give you upto 35% N2/3.

[Kengineer-130]

Stick on heat sensitive patches are a very good little gizmo, stick them in the area suspected of leaks, and see what colour they go to determine if you have a hot air leak etc. :ok: