Category Archives: Foxbat Technical

These posts are mainly about aviation & Foxbat technical and operational information

Incipient spin training

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G-ASBU – the aircraft in which I learned about spinning

When I learned to fly – all those years ago – spin recovery training was a mandatory part of the PPL syllabus. Unless we could demonstrate fully developed spin recovery, left and right, with and without flap, we would not pass the PPL test – simple as that.

Our initial training was on Piper Colts, an aircraft that would just not spin – a spiral dive maybe, but not any kind of real spin. So to fulfil the syllabus, we were required to go spinning in an aeroplane called a Beagle Terrier – which,  like its doggy namesake, displayed an interesting mix of mongrel and pedigree behaviours. The Terrier is at heart an Auster and like many 1940’s and 1950’s British aircraft, would bite you like a rabid dog, if provoked.

Every weekend, an RAF Wing Commander used to bring his little Terrier to the airfield for us very green students to go spin training. The procedure was to climb to 6,500 feet, do a few straight stalls and then start the spins. So, after clearing turns and carb heat to hot, we powered back to idle and slowly pulled back on the controls as the aircraft slowed down. Then, just as the nose started to drop in the stall, it was a time for a big bootful of right or left rudder and over we went. Wait for the WingCo to give the word and then opposite rudder to stop the spin and gently pull out of the dive, carb heat to cold and begin to apply power. The minimum number of turns in the spin before recovery action was three. Sometimes the WingCo went for four or even five turns before issuing the ‘stop’ order – always with a great big grin.

Learning spin recovery techniques was a bit scary at first – on occasion, the Terrier would go right over on its back and seemed to rotate about a point somewhere above (below?) your head and outside the plane – but as we gained in experience, all the students came to realise that knowing what to do in these circumstances improved our flying hugely and gave us more confidence to know we could handle at least some of the unusual flying attitudes which can occur in an aircraft.

Somewhere along the line, somebody in officialdom decided that it was either too dangerous to continue spin training or that it just wasn’t necessary with ever evolving safety in aircraft design – after all, even the old Colt couldn’t be provoked into anything like a real spin. Or both. Anyway, the training was changed to recognising potential spinning events and avoiding them. Or ‘incipient’ spin training. Which was probably a bad decision.

Recently, there has been a great deal of discussion and concern following an unfortunate incident in a certified aircraft conducting incipient spin training, as currently required per the CASA Part 61 Syllabus.

With it, there seems to be a lot of misunderstanding about the definition of what actually is an incipient spin, and it seems that even the local regulators have some difficulty defining it. Nevertheless, many (wrongly) assume the term to mean a stall with wing drop.

However, the generally accepted definition of an incipient spin is the transition phase during which a stall is propagating towards a developed spin – which, in some aircraft, may take up to two revolutions.

Remember that if the angle of bank exceeds 60 degrees or pitch exceeds 45 degrees from the horizontal, you are already outside of the allowable flight envelope of all LSA aircraft and therefore considered to be conducting ‘aerobatics’ under CASA’s definition.

Here’s an extract from FAA AC 61-67 “Stall Spin Awareness Training”:

Normal category airplanes are not approved for the performance of aerobatic maneuvers, including spins, and are placarded against intentional spins. However, to provide a margin of safety when recovery from a stall is delayed, normal category airplanes are tested during certification and must be able to recover from a one turn spin or a 3-second spin, whichever takes longer, in not more than one additional turn with the controls used in the manner normally used for recovery, or [alternately] demonstrate the airplane’s resistance to spins.[ie you can’t spin it, whatever]

In addition, for airplanes demonstrating compliance with one turn or 3-second requirements, LSA requirements are:
– similar to the normal category but with less stringent requirements eg aggravated use of controls for FAR 23
– designed only for a margin of safety in delayed recovery from a stall. Therefore not intended for incipient spin training. [Remember, as above, an incipient spin is one which is recovered with the first 1-2 turns of the spin.]

While we are still awaiting a clearer definition from the regulator and would like to reiterate that no initial spinning is approved for the A22 or A32, the Aeroprakt factory does provide a declaration of conformity with the current Part 61 syllabus, with regard to incipient training, as follows:

“Both A22LS and A32 were tested for spins. A special feature of the A22/A32 wing is such that during a classic method of spin entry when the pitch and yaw controls are deflected fully, simultaneously, the aircraft would not spin more than 180 degrees. After which the aircraft recovers from a spin to a steep spiral dive with increasing speed and normal acceleration (G-factor) in spite of the [continuing] fully deflected pitch and yaw controls.

If the controls are still kept fully deflected, then by the end of the second turn of the spiral dive, the load factor will reach +4.0G’s and the speed will increase to Vne.
According to the ASTM (LSA) standard, an airplane may be used for spinning if the load factor and Vne are not reached by the end of the third spin turn.Taking into account the above mentioned, we cannot see any problem in permitting the use of our A22 and A32 aircraft for incipient spin recovery training as described in the CASA Part 61 syllabus, with the only limitation that not more than 1 spin turn may be done.” [11 June 2019]. 

In any case, at Foxbat Australia we recommend that any advance stalling and spin training should be conducted only in an aircraft certified for that purpose. There are many great flying schools around Australia which will allow you to receive proper spin instruction in a certified aircraft.

Whatever, if you like spinning, aerobatics, or neither(!) we highly recommended any pilot to learn more about them and experience them from the pilot seat.

 

STOP PRESS: CASA (Australian readers only) is seeking views on spin avoidance and recovery training. You can have your say by clicking the link below. NB> The survey closes on 27 January 2020.
https://consultation.casa.gov.au/regulatory-program/draft-ac-61-16-v1-0/

Buying a used Foxbat or Vixxen

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For many pilots, owning their own aircraft is a dream – but to own a new one is often just plain beyond their financial reach. So they turn to the used market and start perusing the pages of the Australian Aviation Trader paper and other aeroplane sales websites. Buying a used aircraft – like any used vehicle – is potentially fraught with risk, so here are a few guidelines about buying a used Foxbat/Vixxen – or indeed any other used aircraft.

Overall, the first rule of buying a used aircraft is let the ‘Buyer Beware’. The purpose of these guidelines is not to stop you buying your dream (although there are a couple of red flags) but to ensure you go into the purchase with your eyes open and are fully aware of what you are taking on. You don’t want any nasty – expensive – surprises to ruin the joy of owning your first – or next – aeroplane!

Whatever else, get a completely independent, appropriately licensed engineer to inspect the aircraft and its documentation and give you both a verbal summary and a detailed written report. The engineer should not be associated in any way with the vendor or dealer selling the aircraft. Although a thorough inspection may cost you up to A$500, it could save you ‘000s.

Apart from all the usual things to look at on a used aircraft, be sure to ask the engineer to check for:
– complete service records and any accident damage history.
– all applicable airframe and Rotax engine (see below) service bulletins have been complied with.

In particular, for Foxbats & Vixxens:
– rudder cable bulletin (A22L & A22LS)
– nose leg hinge bracket bearing bulletin  (A22LS & A32)
– windscreen cracks  (A22LS & A32)
– flaperon cardan rings  (A22L & A22LS)
– seat belt correct installation (A22L & A22LS)
(all bulletins are on our website at https://www.foxbat.com.au/safety-bulletins.html)
– the flap lever detente plate (A22LS & A32), which holds the flaps at their chosen setting. This plate is a wear item replaced on condition and if too worn can allow the flaps to retract without warning.

Ask the vendor what the primary use of the aircraft has been – commercial flying training? Private and leisure? Farm work? Ask the vendor if there has been any incident/accident damage to the aircraft and if so, who carried out the repairs. Remember to write down responses, as the answers to all your questions will form part of your contract to buy, should you decide to go ahead. Be very wary of vendors who do not know answers to your questions or who try to give you vague non-specific answers with phrases like: ‘I think…’ or ‘I believe…’ or that catch-all ‘Come and have a look for yourself…’ If they don’t know an answer, OK – but they should offer to get back to you with a clear reply.

Here is something important to check for all used Light Sport Aircraft (LSA).
LSA regulations mandate that any change to the aircraft from its original delivered specification must be explicitly agreed by the aircraft manufacturer. Changes include virtually everything to do with the aircraft – for example: tyre sizes, propeller, instruments, avionics, damage repairs, type of coolant, GoPro and other camera mounts, lighting changes, addition or removal of a parachute, etc etc. Some manufacturers – including Aeroprakt – give blanket approvals for aircraft damage repairs ‘carried out by suitably licensed engineers’ but any other changes must have factory approval first. If not, the aircraft automatically reverts to ‘Experimental’ status until either approval is given or the modification is reversed. LOAs can only be issued by the manufacturer – there is no other authority approved to do this.
Therefore, get a written statement from the vendor either that the aircraft has not been modified after original new delivery or that if it has, specific Letter(s) of Approval (LOAs) have been issued – and are attached with the statement.
If they are not willing to do this – walk away! Any problems will become yours if you buy the aircraft.

For the Rotax engine check the following:
– All applicable Rotax service bulletins have been completed. To check the bulletins, enter the engine number on the Rotax Owner website – https://www.rotax-owner.com/en/ – (click on ‘Does your engine comply with all required bulletins?’ in the page header), enter your engine type (all our aircraft use 912ULS engines), and then the engine serial number. The site will list the bulletins you need to check.

– The total running time for the engine is recorded correctly. For example, the original engine may have been time-expired and changed for another engine – which was new? Or used? Get a confirmation that the time quoted is engine running time, not flight time as Rotax warranties and service requirements are all based on engine running time.

– When the next 5-year rubber replacement is due. This costs in the region of A$2,500-A$3,000 to complete, with parts and labour, and covers all oil, fuel and coolant hoses, carburettor rubbers, fuel pump etc on the aircraft.

– Has the engine been run primarily on Avgas or Mogas? If Avgas, there should be a clear record of oil and filter changes at least every 25 hours, as per Rotax maintenance recommendations. If not, there is no certainty the engine will reach its 2,000 hour expiry time.

– When was the last time the gearbox slipper clutch tension was checked? Is there a clear maintenance record of this?

– Has there ever been a prop strike? If so, the gearbox slipper clutch should have protected the engine. However a power-on prop strike has been known to twist the crankshaft. Any prop strike, however apparently minor, mandatorily requires the gearbox to be checked and overhauled by a qualified Rotax engineer.

Finally, here are a few general guidelines:
– Has the aircraft been parked outside or kept in a hangar? Ultralight and Light Sport Aircraft are necessarily built more lightly to enable compliance with strict weight limits. They do not thus fare well when left outside in the elements, even when properly tied down and the controls correctly secured. Look for water damage inside the aircraft. Do the controls feel ‘sloppy’ because the wind has slowly but surely worn away at the control bearings? Think of the aircraft rocking in the wind for a couple of years…

– Has the aircraft been used in a school or club? Remember, a school aircraft will have probably completed at least 5 times as many take-offs and landings for the same hours as a privately owned aircraft. Depending on the quality of the instructor(s) this might mean anything from not much at all, right through to dozens of (very) hard landings at the hands of poorly managed students.

– Get a written statement from the vendor that the weight and balance information shown in the aircraft documentation – particularly the empty weight – is correct. If the vendor is not prepared to give this statement, walk away!
This is important for your load calculations and your insurance validity.

– The asking price of the aircraft should reflect all the factors above. A single private-owner hangared aeroplane with no damage history, a few hundred hours on the clock and a complete maintenance record, with all the original manuals and documentation, will command a significantly higher price than an aircraft with all the opposite characteristics. Foxbats and Vixxens have an enviable reputation for holding their prices but do not let this general reputation sway your careful examination of the aircraft. Hour-for-hour, the difference in price between a good one and a bad one could be as much as 50%.

Don’t forget the saying: ‘buying cheap can be the most expensive thing you ever do’.

Foxbat 2020 updates for Australia

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For 2020 we are introducing some updates to the A22LS Foxbat/Kelpie and A32 Vixxen aircraft available in Australia while keeping prices at the same levels as for 2019.

First among these is a new windscreen design, using moulded 3mm acrylic instead of the flex-to-shape 2mm flat polycarbonate sheet. The acrylic windscreen is more rigid than the original design, which has served us well for over 20 years. The main benefit is noise reduction in the cabin, particularly noticeable in the A32 Vixxen, which is already a relatively quiet aircraft. There are a couple of minor downsides – the acrylic screen needs special jigs both for original installation and when a replacement screen is fitted; it’s also more expensive than the original, flat sheet design. All new A22LS Foxbats/Kelpies and A32 Vixxens built for Australia after 01 January 2020 will be fitted as standard with the new type of screen.

Although replacement polycarbonate screens will continue to be available, a retro-fit acrylic screen kit will also be available for owners wishing (optionally) to replace their existing polycarbonate screen, should it become damaged. For a returnable deposit, Foxbat Australia will be able to loan your qualified engineer a set of jigs to enable the replacement. We are also making a short video to cover installation of the new screen.

Next, the A22LS Foxbat will now have as standard the so-called ‘Kelpie’ metal luggage bay with side door. We have sold 20 of the Kelpie variant since we introduced it around 2 years ago and in addition, most Foxbat buyers have opted for the Kelpie bay over the previously ‘standard’ canvas luggage container. The main reason for this is probably that the metal luggage bay is rated at 30 kgs maximum as opposed to the canvas container at 20 kgs. The contents of the container remain accessible in flight and a hard cover is included if in-flight access is not required. There is a small basic weight penalty but as the A22LS is already one of the lightest (and strongest) LSAs on the Australian market, you will still be able to carry over 200 kgs of people and bags, even after filling full with fuel.

We have offered a variety of VHF radios over the years, including the popular German Filser/Funkwerk OLED radio. However, after extensive experience with TRIG – a UK (well, Scotland actually) manufacturer – we have decided to include the TRIG TY91 VHF radio as standard on all A22LS and A32 aircraft in Australia. Where optionally requested, the TRIG TT21 mode S transponder will visually match the TY91 radio. Dynon SkyView equipped aircraft will continue with the Dynon VHF radio.

For 2020, all A22LS Foxbats with the Y-stick control configuration will now standardise on the ‘long leg’ raised instrument panel. This panel has curved cut-outs along the bottom edges on pilot and co-pilot side, facilitating comfort for those owners with longer than average legs.

The ‘long-leg’ option isn’t available with twin-yoke configuration controls as the yokes support structure occupies some of the space taken by the cut-outs in the panel bottom. Also, for the A22LS Kelpie, the UHF radio is normally fitted under the panel on the co-pilot side. If you require the long-leg cut out on a Kelpie, there will be a small additional charge to cover installation of a remote head for the UHF radio. The A32 already has legroom equivalent to the A22LS ‘long-leg’ panel.

We are working with the factory to offer a number of additional options on A22LS and A32 aircraft. Among these are a visor-style tinted sun screen in the top of the windscreen, larger capacity fuel tanks for the A32 and a glider tow-hook for the A32. We are also hoping for a supplement to allow doors off flying in the A32 to match that of the A22LS.

As an aside, although we are sometimes asked by customers if they can fit bigger tyres to the A32, it is unlikely these will be formally approved by the factory any time soon. From experience with flying school owners who have removed the wheel spats and leg fairings, we are aware that this can reduce the cruise speed by as much as 9-10 knots, effectively pulling the straight and level cruise of the A32 down towards to that of the A22LS. The A32 is fitted standard with aviation grade AirTrac 15×6.00×6 tyres and landowner experience has shown that these are more than sufficient for use on paddock and gravel strips with the spats remaining in place.

SPECIAL OFFER – for a limited number of aircraft we will include a Garmin Aera 660 GPS with a panel mount of your choice at no extra cost. First come, first served!

For more information on any of these items, please see our website at www.foxbat.com.au  or call Ido Segev on 0431 454 676 or Peter Harlow on 0413 900 892.

Low flying

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Just recently, there seems to have been a spate of low flying accidents in LSAs and ultralights, some of which have involved even experienced low level pilots. And a couple of incidents where the pilot had no low level approval or endorsement. And I’m not talking about landing or take-off accidents.

A lot of LSAs and ultralights – including Foxbats and Vixxens – are bought by landowners for use on their properties – which sometimes includes low flying. By which I mean at heights often well below the 500 foot (normally) legal minimum height. Landowners can fly at any height over their own land.

However, there is a safety reason for the 500 foot height limit – even a small error made at heights under 500 feet can rapidly develop into a major disaster unless you have the right training to avoid and/or quickly correct. The risks rise exponentially if you’re flying at heights as low as 100 or 200 feet, and losing concentration even for a second or two can be catastrophic. Add in slow flight, obstacles, wires and wind and you really need to know what you are doing at low level.

So, first off – if you’re going to do low flying at all, GET A LOW FLYING ENDORSEMENT! There’s a lot more to flying close to the ground than at first you may think. See CASR 1998, Subpart 61.Q – Low‑level ratings, for the main requirements.

Both CASA and RA Australia have published clear requirements for low level flying endorsements both of which have minimum flying hours on type and passing a flight test – normally after a minimum of 5 hours’ instruction at low level on type. To stay legal, there are also currency requirements – eg completion of at least 2 hours of low level flight during the previous 6 months – and flight review requirements, eg CASA requires an instructor flight review for the low level endorsement every 12 months to ensure you retain the skills needed. RA Australia also requires the pilot to give good reason why they should have a low-level endorsement in the first place.

Second, if you have a low level endorsement and you plan to fly low on a regular basis, it is highly recommended that you WEAR A HELMET! In another life, I used to ride a motorcycle for a couple of hours every day. We had a saying then – ‘if you’ve got a $10 head, put it in a $10 helmet…or even better, save your money!’ Now I don’t know about you but I reckon my head is worth a lot more than $10 (some might argue otherwise), so make sure it’s a good quality helmet with a good quality headset.

Unlike motor vehicles, most aircraft – certainly LSAs and ultralights – are not fitted with airbags. However well designed to absorb impact, an airframe can only do so much to protect you. As your head can so easily be injured, protect it with a helmet!

Third, MAKE SURE YOUR PLANE IS IN TOP CONDITION! The last thing you want when you are flying close to the ground is an engine failure or some part of the airframe or control system to malfunction. It is highly likely that there will just not be enough time to recover before the ground rises up and hits you. Regular maintenance – even more frequently than required – and a sharp eye for any abnormalities in the aircraft are one of the keys to keeping yourself safe.

Finally, MAKE SURE YOU ARE IN TOP CONDITION yourself. We have all heard about ‘Human Factors’, we even had to pass an exam on them to get our license. So, to remind you, if you’ve been on the booze the night before, you’re taking medication that could affect your concentration or you’re feeling unwell in any way at all – don’t fly! Something else to remember – when you are low flying, you need a lot more concentration than plain ordinary flying. You’ll need to take regular and frequent rest breaks.

When you are a pilot, low flying can be very exhilarating. But it’s also very dangerous. However easy it looks, make sure you have the right training, your aeroplane is in perfect flying condition and you are 100% fit and ready. And, for what it’s worth – wear a helmet!

Happy (low) flying!

Aeroprakt world record again!!!

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Once again the Aeroprakt team under Yuriy Yakovlyev has posted another ratified world record for distance covered on a measured amount of fuel.

This time, the famed A-40 with two people on board covered 887 kilometres – 479 nautical miles, 551 statute miles – on only 26 pounds/11.8 kilos/17 litres – of fuel. That’s just about 2 litres per 100 kilometres.

Non-stop flight time was 9.1 hours.

For reference, even a very small car will use 5-6 litres/100 kilometres.

For an aircraft, propelled by a standard Rotax 912 series petrol engine, these figures are truly amazing. Once again – congratulations to Yuriy Yakovlyev and his team at Aeroprakt on their wonderful achievement.

Aeroprakt grabs world record with A-40 aircraft

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Yuriy Yakovlyev – CEO of Aeroprakt Limited – and his team have done it again! Not content to rest on their laurels after winning gold medals in two major light aircraft championships this year, they have now landed a world record.

Their A-40 competition aircraft – adapted from the well-known A20 tandem 2-seat taildragger in pusher prop configuration – has achieved a staggering and authenticated 229 kilometres on just 8.5 litres of fuel. In imperial measures, thats over 142 miles on 2.25 US gallons; over 63 miles per gallon, 3.7 litres per 100 kilometres!!

Whichever way you measure it, it’s an amazing feat for a 2-seat aircraft using a standard Rotax 912 series engine – no batteries or electric motors. Pilot and co-pilot for this extraordinary accomplishment were Yuriy’s son Timofey and engineer Taras Sotnicenko. Looks like Timofey has his father’s genes.

Very big congratulations from Foxbat Australia to all involved!

You can follow the maestro Yuriy on his FaceBook page by clicking here.

Foxbat Australia – new website coming!

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After almost 5 years with our current website at www.foxbat.com.au we have developed a new, much more modern site design for Foxbat Australia which will be going live in the next week or so.

Although the old website has been widely used and favourably commented on, apart from making it more visually attractive, we have aimed to make navigation simpler – particularly for the many visitors seeking technical specifications and maintenance information.

All the details from the old site have been retained and updated, including the ever-popular ‘Used Aircraft‘ page, which is statistically the most visited single page on the site! In addition, if you want to find a school or club in Australia using Aeroprakt aircraft, we have introduced a clickable map to help you find one near to you.

There are also additions of an in-site photo and video gallery, so you don’t have to navigate away from the site to see visuals. However, our linked Foxbat YouTube channel and Foxbat Facebook Page will remain in operation – have a look, we post new items regularly on Facebook and are planning more YouTube videos over the coming months.

Once the new site is up and running, feel free to send me your comments!

Foxbat & Vixxen nose leg maintenance

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Due to a recent failure of a nose landing gear leg lower support bracket, we would like to remind all owners of A22LS Foxbat, Kelpie and A32 Vixxen to make sure all regular maintenance is complied with in full and in accordance with their specific aircraft maintenance manual requirements. The landing gear system can be easily forgotten or overlooked during maintenance and during the daily pre-flight inspection, however, it is important to closely inspect all of its components.

How does this affect me?
The A22LS Foxbat and A32 Vixxen Aircraft Maintenance Manual (AMM) requires 100 hourly checks of the landing gear system, with a specific requirement for inspection and greasing of the lower fork attachment bracket and bellcrank due to its trailing-link operation. While the failure record on flight school/club aircraft averages over 7,000 landings, this inspection and maintenance action should be carried out by all owners and operators on a regular basis.

Aeroprakt will shortly issue an official service bulletin with a recommendation for inspection of the lower attachment bracket, however, in the meantime please find here a short guide which is intended to provide additional information to ensure the correct method is used. Failure to comply with the AMM inspection may result in the pivot bolt seizing and a failure of the lower attachment bracket.

Please note: It is not sufficient to lubricate this bolt/bracket with silicone or lithium spray. Please use the correct heavy duty anti-corrosion grease as instructed!

The guide can also be found on our website under Maintenance & Technical > Aircraft Maintenance Information.

If you don’t already receive our regular newsletter and information emails, please make sure you are on our mailing list – to subscribe simply email us at info@foxbat.com.au so we can add you

The elephant in the aeroplane

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In Light Sport Aircraft (LSAs) and Recreational Aviation (RA) – indeed in all flying machines – weight is a key factor. In fact it could be said that weight is THE factor when it comes to light aircraft design – strong (meaning heavy) enough to do the job, yet light enough to carry a reasonable load within the legal regulations of its category. Of all categories, LSAs and RAs have probably the most stringent weight limits applied to them.

Yet in almost all LSA/RA flight reviews I read, there is little or no mention of usable load, empty weights or maximum gross weights. How come nobody discusses this key topic – the elephant in the room? The aircraft may look and fly great but if the usable load is so limited that carrying a couple of typically sized people and a reasonable amount of fuel will take you outside the legal limit for the aircraft – what use is it?

At the recent Avalon Airshow, I wandered around looking at a wide selection of LSA and RA offerings. Many of them were kind enough to display data including empty and maximum weights alongside the aircraft.

All the aircraft I looked at posted a maximum gross weight of 600 kgs or, in a couple of cases, 550kgs and 544kgs. There was a seaplane with a maximum of 650kgs.

The declared empty weights varied between 312kgs and 530kgs although one of them went to the trouble of blanking out the empty weight for some reason. Excluding the anonymous empty weight and the 530kgs machine, the average empty weight of all the LSA/RA aircraft I photographed worked out at a whisker over 360kgs.

One well-known LSA showed – for what appeared to be identical models – empty weights of 360kgs and 390kgs. What, I wondered, could make such a large difference? there appeared to be no parachute rescue system in either, so I (at least) was puzzled.

So let’s have a look at usable loads. Taking a maximum gross of 600kgs, minus the average 360kgs empty weight, leaves you with 240 kgs for fuel, people and baggage. Typical pilots these days tend to weigh in at around 95+ kgs, passengers anything from 60 -100kgs+ – a total for people from around 165-195kgs. Some would say I’m being optimistic! I have certainly seen two big 100kgs+ people get out of an LSA on many occasions. But let’s stick to an average of 180kgs total for people. That legally leaves about 60kgs for fuel and bags. Fuel weighs around 0.72kgs per litre, so without bags you have about 80 litres of fuel. As an absolute minimum, you probably need to allow at least 5kgs for ‘bags’ – remember, tie-down kit, maps, aircraft cover, removable navigation/GPS equipment, headsets, cameras, clothing etc all count as ‘bags’.

Worst case scenario: your aircraft empty weighs 390kgs – see above. You weigh around 100kgs with your boots, headset and clothes on, your passenger the same. You’ve got a 2kgs tie-down kit in the back and your trusty portable GPS on board, plus your passenger’s camera kit. It all adds up to well over 590kgs – leaving less than 10 kgs for fuel, or around 13-14 litres….any more and you’re flying illegally in a 600kgs maximum gross aircraft.

So, what can you do with the elephant? Setting aside the regulations for the class, which lay down maximum empty weight limits based on engine power and number of seats, what implications does this have for buyers and, in particular, flying schools, who want to stay within legal load limits?

First, make sure, before you buy, what is the actual empty weight and thus the usable load. Beware of statements like ‘from 295kgs’ as this weight is often an absolute factory minimum, with no oil, or battery, or bigger ‘standard’ wheels/tyres, wheel spats, radio, antenna, even (in one case I know of) seat cushions and flight instruments. Don’t accept assurances that the factory already weighed your aircraft so you don’t need to – I know of a number of occasions where a repaired aircraft had to be re-weighed and came in much heavier than before repair – in one case somehow gaining over 40kgs (yes, really!) compared with the original factory weight sheet.

Get a written guarantee of the empty weight of the aircraft you’re buying or ask for the aircraft to be weighed just before you take delivery, it’s worth the money – and remember, the manufacturer wants to sell you an aircraft and won’t be the one copping it when you get ramp-checked, or the insurance company refuses to pay out because the plane was flying over the legal weight limit. Or your flying school is audited with a random weight check.

Next, work out your true weight and that of your passenger/co-pilot – including boots/shoes and clothing. Add that to the real aircraft empty weight to work out how much fuel and baggage you can carry. Can you still carry full fuel as well as people and bags? If not how much are you prepared to compromise? Personally, I have a 2-3 hour bladder, so I don’t often need full (fuel) tanks. But what about that 2-hour flight to a place with no fuel, plus the journey home?

Even if you and your passenger are quite light, remember that when you come to sell the aeroplane, the customer might be a flying school, or a lot heavier than you, potentially limiting your sales options.

There’s another one I hear a lot: ‘the plane’s safe to 750kgs gross, so you don’t need to worry’. But you DO. Safe it may be, legal it’s not…remember ramp checks and insurance companies?

Last but not least is the issue of centre of gravity (CofG). The CofG limits are calculated to fit in with the maximum gross weight of the aircraft – how many owners/pilots of LSA/RA aeroplanes actually calculate the CofG before taking their (maybe slightly heavier) friend for a quick morning flight? Tanks full? Feels a bit slow to lift off? Or maybe too quick, with a rearward CofG? No problem, the plane will fly OK…until it doesn’t. Read some accident reports about exceeding CofG limits.

Some people might feel I’m being a bit picky – after all, how often do you get ramp checked? Or insurance companies weigh the aircraft before paying out? Actually, surprisingly often. But the laws of physics can’t be denied; if you frequently fly at or over the aircraft weight limit, it will wear out much quicker. Safety margins are compromised and the flying characteristics will become more and more like a heavier GA-type aircraft. The cruise will be slower, the stall will be higher and you stand much more chance of bending the landing gear if you come down a bit heavy.

Ignorance of the true empty weight of your aeroplane is no defence. Don’t ignore the elephant! You have been warned!

Testing an Airmaster constant speed propeller on the Foxbat

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For the last 45 flying hours, we have been evaluating an Airmaster electric constant speed propeller on our Aeroprakt A22LS Foxbat demonstrator and comparing it with the standard on-ground adjustable 3-blade KievProp.

For those of you not familiar with the New Zealand manufactured Airmaster prop, it is a superbly made and easy to use piece of kit. This particular example was retro-fitted after the aircraft arrived in Australia and installation was straightforward. It is a Rotax mandatory requirement that a manifold pressure gauge is fitted with a constant speed propeller, so this was included too.

After discussion with Airmaster, the prop was fitted with three WWR70Z Whirlwind blades, with an overall diameter of 1775mm (about 70″).

Operation of the prop pitch is via a control unit on the instrument panel (it fits into a standard 2.25″ hole), which connects electrically with a motor inside the prop hub, which changes the pitch of the blades. The control unit has a rotating knob with four settings: ‘Take-off’, ‘Climb’, ‘Cruise’ and ‘Hold’. For the Rotax 912ULS engine, these settings correspond to full power RPM values of 5800, 5500 and 5000 respectively. The ‘Hold’ position keeps the RPM to whatever setting you choose, so long as the pitch angle can accommodate. There’s also a small up/down switch for ‘Auto’ and ‘Manual’ operation. Finally there’s a separate spring loaded pitch toggle ‘coarse/fine’ switch which enables you to change the pitch manually. [The evaluation propeller did not have the ‘Feather’ setting on the rotary switch as shown in the photo – this is intended for use on motor gliders. However, the propeller can still be feathered by holding down the lower switch for 5 seconds. There is also a controller with a reverse setting, aimed at seaplanes.]

In normal use the system is very simple to operate – when you’re lined up on the runway, ensure you’ve set the switch to ‘Auto’ and dialled up ‘Take-off’ and apply full power. The engine revs to its 5800 redline and the aircraft takes off like a scalded cat! At about 200 feet above ground, still on full power, rotate the dial to ‘Climb’ and the RPM drops back to 5500, the maximum continuous RPM for the 912ULS. Finally, when you are ready, dial in ‘Cruise’ and throttle back as needed. At altitudes below about 2500 feet we tended to adjust the ‘Cruise’ throttle to give about 25-26 inches of manifold pressure at 5000 RPM.

As an additional piece of information, we checked the static thrust of the Airmaster propeller at full throttle and 5800 RPM, using a calibrated strain gauge, and compared it with the standard KievProp at the same static full throttle RPM.

So, what did we find?

At 5800 RPM on full throttle, the Airmaster developed around 200-205 kilograms of static thrust, compared with about 195-200 kilos from the KievProp. When you take into account that the Airmaster prop is about 12.5 kilos heavier than the KievProp, at these RPMs and power settings, the props were in effect generating about the same thrust per kilo of aircraft weight.

In comparison with the KievProp, the Airmaster gave similar take-off distances and climb rates, although the KievProp had a slight edge above 200 feet, as it remained at 5800 RPM compared with the Airmaster 5500 ‘Climb’ setting. Rotax allows a maximum of 5 minutes running at 5800 RPM, so if you’re in a hurry, you can leave the prop/engine running at this speed. For both the Airmaster and KievProp, 5 minutes at 5800 RPM will get you well over 5000 feet above your take-off point!

When joining the circuit for landing, we reduced power and changed the prop setting in stages – ‘Cruise’ around the middle of downwind, ‘Climb’ at the start of base and ‘Take-off’ somewhere down final approach, so that full power was available in the event of a go-around. The Airmaster gave a noticeable ‘airbrake’ effect when moved to fully fine pitch, increasing the descent angle. Similarly, in the event of an engine out glide, it would be a good idea to set the prop full coarse (or even feather it) with the manual setting, to reduce drag from the stopped or windmilling prop.

The main differences come out at the ‘Cruise’ setting of 5000 RPM. At this setting the Airmaster gave a steady 95+ knots True Air Speed (TAS) – we are lucky enough to have a Dynon D10A on our panel, which shows TAS. The fixed (on-ground adjustable) KievProp set to give 5800 RPM on take-off could only manage around 80+ knots in the cruise at 5000 RPM. However, when set to the factory recommended pitch (giving about 5100 RPM on take-off) the KievProp will at least match the Airmaster cruise speed at 5000 RPM, although take-off and climb will not be quite as spectacular.

And there you have it in a nutshell – the Airmaster will give you great take-off performance and a good cruise speed in the same flight. The standard fixed-pitch KievProp you can achieve fantastic take-off performance or a good cruise speed, but not both in the same flight. However, the ‘factory’ setting will at least match (and maybe even exceed) the cruise speed of the Airmaster, albeit with a small dent in the take-off distance and climb out rate.

Whether the Airmaster is worth losing around 12.5 kilos of load capacity and a cost of around A$13500 (about US$9750) including GSTax, installation and manifold gauge, is a question only each individual owner can answer.