Light Sport Aircraft Maintenance

It is my belief that today’s recreational and light sport aircraft need more careful and meticulous maintenance than traditional ‘rag & tube’ ultralights and typical single engined GA aircraft.

Over the last 15-20 years or so, recreational and light sport aircraft have become much more GA-like in their looks and construction, compared with traditional utralights of old.

Their weight and complexity has increased almost beyond the imagination of early ultralight owners; their airframes have become more and more GA-like, with concealed control systems, engine bay ducting which hides many key engine components, digital instrumentation, auto-pilots and the like. Yet recreational aircraft owners and pilots are still permitted to ‘do all their own maintenance’*.

Crucially, recreational and light sport aircraft have to be designed and built to fit under a specific gross weight limit. There is also a maximum empty weight formula related to the maximum gross, which effectively limits the empty weight of a 2-seat aircraft to around half that of a typical 2-seat GA aircraft. As a result, manufacturers have to do everything they can to minimise empty weight – usually by using light weight materials and making components as strong as they need to be, but no stronger.

This lightweight approach is not in itself an issue – indeed it has enabled the design and manufacture of some wonderful aircraft. But in reality, ‘cheaper and lighter’ means you have to be much more thorough with your inspections and maintenance.

Why?

Because the metal is thinner all round; because so-called ‘carbon fibre’ aircraft actually contain very little carbon fibre (if they really were mainly carbon fibre, their cost would be astronomical); because cables are thinner, because engines are smaller/lighter/more highly stressed, because propellers are typically composite not metal; landing gear is lighter; bearings are smaller, tolerances are tighter; and because some of their systems are quite different from typical GA aircraft, and on and on…

Although RAAus is working wonders to improve the safety of aircraft registered with them – particularly focussing on maintenance issues and authorisations to maintain*, I still have considerable doubts as to the maintenance capabilities of many RAAus Aircraft owners, who likely have little or no aircraft maintenance knowledge and experience. I myself know the A22 and A32 airframes inside out but I do not feel at all confident I could safely maintain one.

For example do these owners know:
– how properly to lockwire a bolt, and what thickness and type of wire is required?
– how to measure and adjust the tension of a control or structural cable?
– how and when to use a torque wrench correctly?
– the standard torque settings for each size of bolt?
– how and when to check static and dynamic carburettor balance?
– how to check the friction on the Rotax gearbox clutch?
– how to make sure the ends of a cable are still securely swaged?
– how to measure correctly the strength of the fabric covering on a wing?
– how to open and examine properly an oil filter after an oil change, and what to look for?
– how to check a control or structural cable for internal abrasion and wear?
– how and where to look for cracks in metal/composite/wooden airframes?
– where to place a jack to raise their aircraft?
– how to decide when to replace an ‘on condition’ item?
– what constitutes ‘acceptable’ and ‘unacceptable’ wear in an item?

Not to mention possession of all the tools needed to do these jobs properly?

Now, I’m aware of many aircraft in our Aeroprakt fleet with well over 3000 hours on them – with no particular problems. As I say, maintained properly, recreational and light sport aircraft can continue flying safely for many thousands of hours.

But if you are going to maintain your own aircraft, get proper training to do so – if you skimp on maintenance or try to save money by doing it yourself when you don’t really have the capability, at the very least your aeroplane won’t last as long as it should. And at worst, it will be your life (or that of the pilot) that’s threatened.

* Owners of RAAus registered aircraft may maintain their own aircraft provided they have an L1 Maintenance Authority (sometimes called an ‘Owner-Maintainer’ authorisation). Details of this are available on the RA Australia website at http://www.raa.asn.au  under the member section ‘Member Training’

So you think light sport & recreational aircraft are expensive to maintain??

SIDS picThose of you bemoaning the ever-escalating costs of keeping your light sport and recreational aircraft in tip-top airworthy condition should spare a thought for Cessna owners.

AOPA Australia has published some information about compliance with the Cessna SIDs (Supplemental Inspection Documents) process, which has been devised to help ensure older aircraft remain airworthy. Unless you have at least a 7-figure credit bank balance, it makes for pretty bleak reading. And, after all, most older planes are owned by people who can’t afford to buy new ones, so the compliance cost is particularly burdensome.

Here’s a few examples relating to the venerable Cessna ‘100 series’ aircraft, ie 150, 152, 170, 172 etc. These requirements have a deadlines looming ever closer – the end of 2015 for commercially used aircraft and end of June 2016 for private aircraft. Cost figures are ex-GST and are only intended to be broad estimates.

SIDs 2CASA AWB 02-048 issue #2 requires that all mandatory and advisory service bulletins concerning the Principal Structural Elements (PSEs) of the aircraft are inspected and complied with. This includes not only obvious and expected items like wing spars and landing gear but also things like door frames and, for example, any areas of the aircraft skin under ‘fore & aft’ and/or ‘circumferential loads’ – ie most of the aircraft. Projected costs for this inspection and typical remedial work are in the A$10k-A$50k range.

In addition, NDBs and VORs have to be decommissioned and VHF radios and nav equipment updated. You’re looking at A$35k-A$55k for new TSO’d equipment. Makes the Dynon SkyView look like very good value…

In addition, AD/GEN/87 Primary Flight Control Cable Retirement (scroll down that page to see AD 87) requires all flight control cables to be replaced every 15 years. Cost estimate A$8k every 15 years. Many aircraft are still operating with the original manufacturer’s cables, even after 30-40 years.

In addition, there is a proposed airworthiness directive (AD/PROP/1A3) which will require regular mandatory strip downs on all constant speed props – cost every 6 years is around A$2k. It is estimated that as many as 50% of these propellers will be deemed unserviceable and have to be replaced, at a typical cost of A$14k.

Finally, after the initial SIDs inspection & remedial work, there’s an ongoing SIDs ‘top-up’ cost of around A$3k a year to keep it all current. On top of any other required maintenance.

If you own a Cessna single engine retractable or, even worse, a twin, you’d better start looking round for a second mortgage on your home – assuming it’s worth enough – because SIDs related costs could be 3-4 times as much as for a ‘simple’ single.

Against these figures, an annual cost of under A$1,000 for a LAME or L2 to issue your LSA maintenance release doesn’t look so bad. And if you get your L1 ticket, you can maintain your RA-Australia registered aircraft yourself. Personally, although I’m doing the L1 with RA Australia online, I want a fully qualified engineer to check out my aircraft at least once a year…