Basic aircraft mechanics, help!

ashyle

Can anyone answer me a few (possible) dumb questions? Tried googling it but I was totally bogged down by all the detail!

50 hour checks on an aircraft (on, let's say, one of these for example). How thorough are the checks and how long do they take to complete? I presume if you keep an airplane at an airfield hangar, they are performed by a mechanic?

No need for a deep explanation just need it as background info

Rubecula

Aircraft checks (be it 50 hour or other) are set down. Each component that is required to be checked or tested or even replaced is laid down in OOPS codes. (Out Of Phase Sevicing). On top of this the persons doing the checks look for other signs of component failure.

If these checks are done properly, and they should be as when signing for doing the job it is a legal document, then everything will be perfectley servicable. The checks are very thorough.

For most aircraft the persons who do the checks are licenced engineers. For the few (mostly military) that do not have licenced engineers carrying out the checks, there is a failsafe method of experienced engineers double checking everything. And the engineer who is in ultimate charge has to be licenced in order to ensure the legalities are fully covered.

That is a pretty basic overview, but I think it covers most of the points.

Incidentally, licenced engineers need to be checked on their work too.

Some jobs require two signatures, some three, and some even more. It really depends on the job involved. No maintenance that I am aware of can be satisfied by one signature.

Do not mistake servicing for maintenance though. A 50 hour service, is basically a maintenance opportunity so it will have many signatures on it for the required tasks. If it is done wrong, the person responsible is held to account both in fact and in legality.

aircraft tech trng

Have a look at page 25 onwards of the following publication. Gives a breakdown of what is required for a 50HR Inspection http://www.caa.co.uk/docs/33/CAP411.PDF

It gives further inspections required if a 150HR inspection and definies the type of check, inspection or test required

Definitions
13.1 Throughout the schedule the following terms and abbreviations have the stated definitions;
Service/Lubrication (Service/Lub)
The term ‘Service or Lubrication’ requires that a component or system should be serviced and/or replenished as necessary with fuel, oil,
grease, water, oxygen, etc., to a condition specified in the appropriate maintenance manual. The term ‘Service’ may also be used to
require filter cleaning or replacement.
Inspect (Insp)
An ‘Inspection’ is a visual check performed externally or internally in suitable lighting conditions from a distance considered necessary
to detect unsatisfactory conditions/discrepancies using, where necessary, inspection aids such as mirrors, torches, a magnifying glass
etc. Surface cleaning and removal of detachable cowlings, panels, covers and fabric may be required to be able to satisfy the inspection
requirements.
Operational Check (OP/C)
An ‘Operational Check’ is a test used to determine that a system or component or any function thereof is operating normally.
Functional Check (F/C)
A ‘Functional Check’ is a detailed examination of a complete system, sub-system or component to determine if operating parameters
are within limits of range of movement, rate of flow, temperature, pressure, revolutions per minute, degrees of travel, etc., as specified
in the appropriate maintenance manual. Measured parameters should be recorded.

ashyle

aircraft tech trng wrote: »

Have a look at page 25 onwards of the following publication. Gives a breakdown of what is required for a 50HR Inspection http://www.caa.co.uk/docs/33/CAP411.PDF

It gives further inspections required if a 150HR inspection and definies the type of check, inspection or test required

Definitions
13.1 Throughout the schedule the following terms and abbreviations have the stated definitions;
Service/Lubrication (Service/Lub)
The term ‘Service or Lubrication’ requires that a component or system should be serviced and/or replenished as necessary with fuel, oil,
grease, water, oxygen, etc., to a condition specified in the appropriate maintenance manual. The term ‘Service’ may also be used to
require filter cleaning or replacement.
Inspect (Insp)
An ‘Inspection’ is a visual check performed externally or internally in suitable lighting conditions from a distance considered necessary
to detect unsatisfactory conditions/discrepancies using, where necessary, inspection aids such as mirrors, torches, a magnifying glass
etc. Surface cleaning and removal of detachable cowlings, panels, covers and fabric may be required to be able to satisfy the inspection
requirements.
Operational Check (OP/C)
An ‘Operational Check’ is a test used to determine that a system or component or any function thereof is operating normally.
Functional Check (F/C)
A ‘Functional Check’ is a detailed examination of a complete system, sub-system or component to determine if operating parameters
are within limits of range of movement, rate of flow, temperature, pressure, revolutions per minute, degrees of travel, etc., as specified
in the appropriate maintenance manual. Measured parameters should be recorded.

Thanks for the reply, do you know off-hand would any of these checks you mention, take less than an hour to carry out on a small aeroplane?
I really just want to use it as *very* background detail in something I'm writing!

ashyle

Rubecula wrote: »

Some jobs require two signatures, some three, and some even more. It really depends on the job involved. No maintenance that I am aware of can be satisfied by one signature.

Thank you for replying! When you say more than one signatory, do you mean more than one engineer has to check over what the primary engineer has already done?

xflyer

Just so you know, as a pilot, therefore clueless and incompetent. I have helped carry out 50 hour checks. But the main thing is that an Engineer, he has checked my work and signed it off. In fact there is no need for me to even be a clueless pilot. I could be a clueless anybody. The main thing is that an Engineer supervises and signs off the whole process.

As a pilot I have the upmost respect for Engineers in part because my brotther is one and in part because I haven't a clue.

aircraft tech trng

ashyle wrote: »

Thanks for the reply, do you know off-hand would any of these checks you mention, take less than an hour to carry out on a small aeroplane?
I really just want to use it as *very* background detail in something I'm writing!

Its one thing carring out the inspections and another rectifing findings or faults. You may have to check say the aileron hinges for play. This alone will take less than 20 minutes. But if play is found in the hindges than replacing them would take a few hours. As was mentioned earlier by another member a 2nd inspection may be required by another engineer. This is called a duplicate inspection and these inspections are normally done whenever a disturbance is made on a system that is a flight control or power control. ie flight controls or engine controls. Regarding the time to carry out tasks varies. Removing the wheels to check the bearing conditions will take 3 or 4 hours but checking seat belt harnesses in the cockpit for security would take minutes................ An operational check of the beacon is just a case of ON & OFF, a minute. Removing the engine spark plugs and checking for condition would be again 2 - 3 hrs!!

What is a DUPLICATE INSPECTION

4.1 The manufactures instructions for continued airworthiness should be followed when determining the need for an independent inspection.

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4.2 In the absence of maintenance and inspection standards published by organisation responsible for the type design, maintenance tasks that involve the assembly or any disturbance of a control system that, if errors occurred, could result in a failure, malfunction, or defect endangering the safe operation of the aircraft should be considered as flight safety sensitive maintenance tasks needing an independent inspection. A control system is an aircraft system by which the flight path, attitude, or propulsive force of the aircraft is changed, including the flight, engine and propeller controls, the related system controls and the associated operating mechanisms.

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4.3 Independent inspections should be carried out by at least two persons, to ensure correct assembly, locking and sense of operation. A technical record of the inspections should contain the signatures of both persons before the relevant CRS is issued.

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4.3.1 An independent inspection is an inspection first made by an authorised person signing the maintenance release who assumes full responsibility for the satisfactory completion of the work, before being subsequently inspected by a second independent competent person who attests to the satisfactory completion of the work recorded and that no deficiencies have been found.

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4.3.2 The second independent competent person is not issuing a maintenance release therefore is not required to hold certification privileges. However they should be suitably qualified to carry out the inspection.

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4.4 When work is being done under the control of an approved maintenance organisation the organisation should have procedures to demonstrate that the signatories have been trained and have gained experience on the specific control systems being inspected.

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4.5. When work is being undertaken by an independent M.A.801 (b) 2 certifying staff, the qualifications and experience of the second independent competent person should be directly assessed by the person certifying for the maintenance, taking into account the individual’s training and experience. It should not be acceptable for the certifying staff signing the release to show the person performing the independent inspection how to perform the inspection at the time the work is completed.

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4.6 In summary the following maintenance tasks should primarily be considered when inspecting aircraft control systems that have been disturbed:

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1 installation, rigging and adjustment of flight controls.

2 installation of aircraft engines, propellers and rotors.

3 overhaul, calibration or rigging of components such as engines, propellers, transmissions and gearboxes.

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Consideration should also be given to previous experience of maintenance errors, depending on the consequences of the failure information arising from an ‘occurrence reporting system’

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4.7 When checking control systems that have undergone maintenance the person signing the maintenance release and the person performing the independent check should consider the following points independently:

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1 all those parts of the system that have actually been disconnected or disturbed should be inspected for correct assembly and locking.

2 the system as a whole should be inspected for full and free movement over the complete range.

3 cables should be tensioned correctly with adequate clearance at secondary stops.

4 the operation of the control system as a whole should be observed to ensure that the controls are operating in the correct sense.

5 if the control system is duplicated to provide redundancy, each system should be checked separately if different control systems are interconnected so that they affect each other, all the interactions should be checked through the full range of the applicable controls.