Record keeping

Tony Carmody's Helicopter Info Site (Sponsored by Rotor Research Pty Ltd)

This site contains knowledge and safety information freely given to enhance the aviation industry. See what our lawyers make us say these days by reading our disclaimer at the bottom of this page - the times are indeed a-changing!

"A little Knowledge is NOT a dangerous thing"

This page is in honour of that rare industry individual who I once heard tell a customer the following dumb phrase:

"What would the manufacturer know - he only designed the helicopter, we fly them!!!".

Finite lives

Definition: The measurable and defined number of cycles or units of time after which it is mandatory to remove a component from service as it may fail/break.

Read: Metal has memory

Fixed wing:

Is not composed of so many moving parts as its rotary wing counterpart. Some have a fixed number of landing or take off cycles on parts of the undercarriage or wing spars. The propeller is often a critical part. Nicks, scratches or overstressing can lead to premature failure.

Helicopter:

Many of the parts used in the construction of a modern helicopter are capable of operating for long periods under severe loads such as in tension, torsion or shear. The problem for designers is to make a part that will be safe for a known number of load cycles yet not be that heavy that the helicopter useful load is reduced to an impractical level or to be too light and have to be replaced after every 50 or 100 hours of use. Intimate knowledge of metal strength and weakness enables the designer to make decisions which are based on the above models.

The designer also uses a theoretical model which assumes that a percentage of time in flight is at gross weight, low weight, full power, low power, high speed etc. After collating all this information, a safety factor is applied to ensure safe operation during normal operations, however the stresses placed on a part through unforeseen conditions such as continuous ops in turbulent mountainous areas or "rough" handling techniques by pilots continually "throwing around" their aircraft during mustering can severely reduce the safe life of a particular component.

Some examples of finite lives are:

Bell 47G Main Rotor Blades: 5500 hours

Robinson R22 Main Rotor Blades: 2,200 hours

Hiller 12E Main Rotor Blades: 6,700 hours

Hiller 12E Main Rotor Tension/Torsion Pin: 643 hours

The time in service of finite life components is tracked and documented from the entries made by the pilots in the aircraft maintenance release log kept in the aircraft. It is mandatory for the pilot to sign it on a daily basis recording that he/she has conducted a daily inspection in accordance with the manufactures requirements and also recorded accurately the helicopter hours in operation.

Hint: If you notice that a pilot is not recording hours correctly or that the Hour meter recording device in the passenger side of a Robinson R22 is not working, then the aircraft is legally un-airworthy as no one would know how many hours the finite life parts have accumulated. The secret is not to be in an aircraft where this is happening in case something lets go as the drop to the ground is usually fatal!

Many outback stations now have a policy of paying the helicopter mustering contractor's invoice only after sighting a signed copy of the helicopter maintenance release with the dates and flight times of the muster exactly the same as those on the invoice. As the great majority of operators are keeping accurate flight records, only the very few operating outside the law - like the person who inspired me to write this article - will object to you asking for a look at their documentation.

If you want to utilise a helicopter operator who is professional and safe, ask the hard questions and you will have no problems.

Tony Carmody