Monday, July 8, 2013

July 8th, 2013

Fresh Air Matters... with Capt. Yaw

I once came across a young aircraft engineer, who felt that he only needed one tool to work on all aspects of aircraft maintenance. He was overly fond of his pliers. He even used it as a pair of pliers – for which I never had a problem. However, when he used it as a hammer, I felt concerned, even if his years of ‘plier-use-as-a-hammer’ appeared to have given him a certain amount of skill in the innovative usage. The use of his pliers as a spanner was something not acceptable in my book. Watching the pretty, golden yellow, corrosion resistant, zinc bi-chromate plating being ripped off the head of an AN5 bolt, with a certain success rate, in regards to bolt removal, concerned me. If I ever saw that happen in our workshops, somebody would be looking for a new job!

The plier is not a tool to be used on bolts, nor nuts – EVER. It is the wrong tool. No, I can’t accept its usage – it is inappropriate. I even have difficulty in permitting the use of an adjustable spanner, specifically if we have the correct tool in the stores and I detect laziness. We have a deep workshop motto ‘use the correct tool for the job’. I look at our tool trollies and realise that the number of ‘special tools’ on the shelves is already many, and growing.

For instance, we have special drill bits, they are 300mm long, and barely 4mm in diameter, we use them to drill a handful of holes in an airframe. They are essential to doing the job properly. There are spanners in metric and imperial dimensions, the same for Allen keys; several different hammers, of varying sizes and materials; screwdrivers with different patterns, lengths and blade tip sizes; cutters for specific purposes, including one that is exclusively used to cut 3.125” (79.375mm) holes in sheet metal below 1.2mm in thickness; a variety of drill bodies and attachments – each one specific in its application and use - and of course, we have a pair of pliers… well, actually more than ten different pairs, sizes and styles of pliers, each for different uses! Each tool has its place, and its job – and it is perfectly formed for its very function.

Our tools are specific to their uses in the aviation industry. They are tools designed for the job they do, and they do them very well.

Any ‘one-tool-thousand-uses’ man is not welcome in our workshops! He may be seen as ‘economical with tools’ by some, but I see him as an accident waiting to happen!

Tools should not be abused (nor should fixations, and materials). Simple.

At this point, sadly, I must offer education on two simple fixation types, and I hope that certain people, working at the Cargo Village in Kotoka International Airport, are reading this.

There exists a simple fixation called a ‘nail’. Generally made out of a metal rod, such as steel, and with one pointed end and the end with a flattened area called the head, suitable for hitting with a hammer. It was introduced for fixing, principally, wooden items together. It could be used to fix wood to wood and also metal to wood. A simple fixation, but with limitations. The ‘normal’ nail has a smooth shaft, and is easily pried open. Some have ridges on them that make them hold a little better. It is not uncommon to see nails used to fix wooden lids to wooden crates. When the lid needs to be removed, a tool called a jemmy (aka pinch-bar, prise-bar, short crowbar, etc.) can be used to lever the lid off of the crate and remove nails. The lid can be reaffixed by careful use of a hammer – however, caution must be applied not to damage the contents of the crate, and then to reaffix the lid properly, it may be necessary to reposition or even replace the nails.

The nail is a very crude fixation device – it is not good in places where you may need to remove and re-insert a fixation, nor in places where ‘banging the crate with a hammer’ may damage the contents of the crate. Therefore a new, more versatile, fixation was developed – the screw.

The screw is more complex and versatile than the nail. It shares some similarities; generally made of metal, one end is pointed and the other is wider and flattened out - called the head. However, the shaft of the screw is shaped with a spiral pattern, from the point, called the ‘thread’. Furthermore, the head has a shape formed into it to allow the screw to be turned, enabling it to be inserted AND removed, several times, without damage and without shock to the joined parts. Screws are more versatile than nails, and can be used with more materials – wood, metal, plastics, etc. – the clever idea being that they are more precise and more controllable in their applications. They are ideal for air-shipped crates containing fragile equipment that may need to be inspected – and the lids replaced carefully, with all contents safely inside, afterwards.

To insert or remove a screw a special tool is used, called a ‘screwdriver’, it is used to drive the screw in, and out, of position – this is a more precise operation than ‘whacking it with a hammer’ and exact forces can be applied, without shock to the components being joined, or contents of a crate, should they be used on the lid of a crate. This ‘screwdriver’ tool has a shaped tip that can be inserted into the shaped head of the screw – and the screwdriver has a special handle, that can be used to turn the screwdriver, and thus the screw, using the human hand. (Powered versions are available also.) The handle is NOT to be used as a hammer - ever. Screwdrivers come in many sizes and tip shapes to suite a wide variety of applications. Most screws either have a flat line in their heads (for a flat head screwdriver) or a sort of cross in their head often called cruciform, with specific styles developed by companies for their uses. The most common cruciform heads are called ‘Phillips’, ‘Pozi’ and ‘star’, and are generally able to be worked on with a common ‘cruciform’ screw driver. With about six screwdrivers - three flat heads and three cruciform - it is possible to remove and insert the vast majority of screws used on the market today – without damage.

I am amazed that so few people grasp the functional and operational difference between a nail and a screw – often damaging the materials used – and in the case of crates, their contents. It is not difficult to grasp, nor difficult to apply – but it is important. However, it seems that there are far too many people who believe that a screw is a type of nail and forcibly rip them out with a jemmy and attempt to re-insert them with a hammer, with impunity – leaving damage behind. There is far too little care for the beauty of the screw, its function, and the amazing capability of the unpretentious screwdriver, as well as screw selection as a frequent fixation method - designed to be reused, without damage to the parts being fixed.

Unbelievable, I know, but true. Education is key, and I hope that this helps those who (now) know about these things to better share such knowledge with those who don’t yet respect the humble screw, its function, purpose and magnificence.

Perhaps we need a nationwide campaign.

Capt. Yaw is Chief Flying Instructor and Chief Engineer at WAASPS, and lead Pilot with Medicine on the Move, Humanitarian Aviation Logistics ( e-mail )

No comments:

Post a Comment