Testing an Airmaster constant speed propeller on the Foxbat

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.

Glider towing with the A22LS Foxbat

Sunday 17 March 2017 dawned clear and a relatively cool 20 celsius at Tyabb Airport. My friend Mike Rudd and I were flying that morning up to Benalla, north of Melbourne, to submit our A22LS Foxbat demonstrator to the Gliding Club of Victoria to test-tow a couple of gliders.

The flight from Tyabb to Benalla was uneventful except for a thick smoke haze up to about 6000 feet due to the smouldering remains of some large bushfires in the area and an almost total lack of wind. About an hour and 20 minutes after take-off, were touching down at Benalla. Gliders were already in the air, albeit in much smaller numbers than the last time we visited, just over 3 years ago.

I flew a short acclimatisation flight with Rob Pugh, the tow pilot for the day (I am not licensed to tow); he made one of the smoothest landings I have experienced in someone who had never flown the type before. Very reassuring for the remainder of the morning! Rob then did a couple of circuits on his own to check out the Foxbat handling without my 85 kilos of ballast in the passenger seat – anyway, towing is only permitted with one person on board.

The first glider – a single seat SZD51 Junior with gliding instructor Steve Hobby on board – was hooked up and, with GoPros activated on the Foxbat, Rob applied full power and took off. Temperature on the ground was about 30 Celsius (about 85-86 Fahrenheit), giving a density altitude at ground level of well over 2500 feet. There was almost no wind at all. Tow time to 2000 feet AGL (2500 feet on the QNH, about 5750 density altitude) was almost exactly 6 minutes and Rob was back on the ground just over 3 minutes later.

Next up was a 2-seat Twin Astir glider with just one person on board. This glider is affectionately known as the ‘concrete swan’ – the heaviest 2-seater in the club, so it would be interesting to see how long it took for the trip. In the event, tow time to the same altitude took only 30 seconds longer and Rob was back on the ground again, around 3 minutes after release.

We are making a short video of the test-towing which will be uploaded to our YouTube channel shortly. Meanwhile, Rob had a few candid comments about Foxbat towing. “Of course”, he told us, “with only 100hp available, the Foxbat won’t be competing with our Pawnees [my note: one of which has a liquid cooled Chevrolet V8 engine!]. But the Foxbat performed very well, considering the lack of wind and the high density altitude. The total take-off to landing times of just over 9 minutes worked out much better than the 13-14 minutes we were expecting. I think the high lift wing really helps it outperform many other Rotax engined types when towing”.

Successful glider towing is a complex equation – it’s not just how long it takes to reach altitude, it’s also the total air time on the tug (based on which, the glider pilot/customer pays), fuel costs, maintenance costs and any depreciation costs on the aircraft tug – many club towing aircraft have been written down to zero in value over the years.

However, the overall exercise was to determine how well the A22LS Foxbat performed – and the answer seems to be ‘much better than expected for such a small aircraft’. This feedback, together with excellent reports from other countries using the A22 for glider towing, confirms our belief that the aircraft will handle 75-80% of  typical towing tasks at around a third of the costs.


High risk turns

Here’s a great video by legend Wayne Handley, all about the use of rudder in turns. Although written primarily for ag pilots, the lessons he gives are equally applicable to pilots who often fly close to the ground – for example when stock counting or mustering – or even just the rest of us when we make that last turn at 500 feet on to final approach to land.

His explanation of what causes one wing to stall before the other is excellent, as are his instructions for spin avoidance and wing-drop recovery.

Although posted nearly 10 years ago, the lessons in the video are just as important today as they ever were! Great stuff from Wayne Handley and a quarter hour well-spent!

As usual, to view the Vimeo video, click on the picture or here: Smart Turn by Wayne Handley

Dan Johnson tests the A32 Vixxen

Light aviation’s guru blogger Dan Johnson grabbed the opportunity to test fly the newest FAA LSA-approved aircraft, the Aeroprakt A32 Vixxen.

Click the photo above or here to see the article and accompanying video: Dan flies the A32

You can read more – much much more – about all manner of light sport, recreational and ultralight aircraft on Dan’s blog: ByDanJohnson.

Why LSAs crash so much

I have long held a view that Light Sport Aircraft (LSAs) are not, as many people seem to think, just less expensive ‘mini’ GA aircraft.

For a start, they are built to much tighter weight tolerances than typical GA aircraft and thus need careful maintenance to ensure that they remain airworthy. Don’t get me wrong – a correctly maintained LSA can have a life span of many many years – but alas, in Australia, quite a few LSAs are quite legally owner-maintained by people who do not really have the skills, experience or knowledge to do so….but that’s another rant.

More importantly, LSAs have quite different flight handling characteristics from typical GA aircraft. This starts with taxiing, where dyed-in-the-wool GA jocks often describe them as ‘squirrely’, through to take-off performance: what typical school GA trainer will take off in 4-5 seconds after applying power, as many LSAs will? In the cruise, the light wing loading of most LSAs (remember, the regulation requires a stall speed limit of 42 knots ‘clean’) is more susceptible to turbulence – although the great upside of most LSAs is that they are a lot more responsive (to some, ‘fun’) on the controls.

This responsiveness, however, can potentially cause problems when it comes to the approach and landing phase of flight. For a start, approach and landing speeds of most LSAs are around 50 knots or even slower, a speed which feels dangerous to many GA pilots. Come in faster and you’ll likely over-control, and/or float or balloon the aircraft, with potentially disastrous consequences.

To further expand our thinking, Paul Bertorelli of AVweb has made a great little video on the subject of accidents in LSAs, which you can view by clicking on the picture above or here: Why Light Sport Airplanes suffer so many crashes

Most of Paul’s statistics refer to the USA market but all of his comments apply to LSAs the world over. Enjoy the video!

Cleaning A22 Foxbat and A32 Vixxen windscreens

Over the last couple of years, we have received reports of broken windscreens on a very small number of Aeroprakt aircraft in Australia. A couple of these were definitely due to bird strikes. However, the cause of a couple of others has never been finally agreed.

The factory reports a very limited number of screen failures in the rest of the world – I believe two or three more – in addition to those reported in Australia. This is out of a total world fleet of over 1,100 aircraft spanning 22 years of production.

In an effort to establish potential causes, and thus introduce preventative measures, we have agreed to publish as much information as possible and seek owner responses where appropriate.

First of all, the factory wants to emphasise the following points:
1. The windscreen design and material have proven themselves on hundreds of Aeroprakt airplanes. Screen collapse cases are extremely rare and have never been associated with the design, but usually pre-existing cracks.
2. Current windscreens are made not of polycarbonate plastic but of PET (Polyethylene terephthalate), so any ‘polycarbonate approved’ cleaner may not be suitable for PET.
3. The effect of unsuitable cleaners (including gasoline, Windex®, Mr Sheen®, solvents which may be suitable for acrylic screens or any other non-PET approved solvents) on the structural properties is such that the PET glass may become brittle (crack-prone) in stressed areas (although in non-stressed areas it has no such effect).
4. The factory does not make oversize rivet holes in the glass because it makes no sense as the rivets compress – that is, produce stress in – the glass anyway.
5. All-aluminium rivets are used to secure the windscreens. This means every part of the rivet is aluminium – including the shaft, which is not steel, as per regular ‘pop’ rivets.
6. The recommended sealant for PET and polycarbonate windscreen replacement is now an acrylic transparent sealer such as FulaSeal 701, not a silicone sealer, which should be used sparingly. Excessive use of sealer can potentially weaken the screen.
7. Finally, a thicker glass is not a good solution as it will be under even higher stress in the areas where it is formed to the required shape. Therefore it will be even more prone to cracking.

In the past, based on local engineers advice, it has been Foxbat Australia’s understanding that the windscreens of A22 and A32 aircraft were polycarbonate sheet and as part of our new owner pack, we have included a canister of proprietary polycarbonate screen cleaner. We have also in good faith recommended these cleaners to existing owners. None of these products expressly forbids their use on PET, nor can we find any information regarding their suitability for PET – indeed, they all make generic statements like ‘suitable for cleaning all plastics’.

However, at the present time, we strongly recommend that owners/pilots of Aeroprakt aircraft stop using these types of cleaner on their windscreens until such time as their manufacturers confirm without reservation and in writing that they are suitable for PET.

So how should you clean your Foxbat/Kelpie or Vixxen windscreen?
1. We recommend cleaning PET (or polycarbonate) plastics first with a mild solution of soap or detergent and warm water. It is also possible safely to use a specialty cleaning product such as Novus® No.1 or Brillianize.
2. DO NOT use window cleaning fluids with ammonia (such as Windex®, or Formula 409®), Mr Sheen®, gasoline, denatured alcohol, carbon tetrachloride, or acetone, which will cause the plastics to craze with minute cracks.
3. DO NOT use so-called ‘aviation approved’ screen cleaners as these may have been formulated for cleaning other types of plastics.
4. Begin by gently blowing away any loose dust, dirt and dead bugs from the surface. DO NOT use a pressure washer on any part of the aircraft, including the screen.
5. DO NOT use proprietary chemicals (such as ‘Bug Off’) to soften and remove dead bugs from the screen. Simply spray a weak solution of soap and water on the screen and let it soak for 5-10 minutes, re-spraying if needed to keep the surface wet. Then wipe with a wet non-abrasive/non-contaminating/lint-free soft cloth, microfibre cloth, or cellulose sponge. Rinse well with plenty of clean, clear water. You may need to repeat this process a couple of times to remove all dried-on dead bugs.
6. To give a final clean to the screen, apply the specialty cleaning product (or a weak soap and water solution) with a dampened non-abrasive/non-contaminating/lint-free soft cloth, microfibre cloth, or cellulose sponge.
7. Rinse well with plenty of clean, clear water.
8. Pat dry with a chamois leather, damp cellulose sponge, or microfibre cloth to prevent water spotting.
9. Repeat this process regularly to ensure there is no build up of dirt on the windscreen. If possible, clean a dirty screen immediately after flight to stop dirt etc hardening during the time before you next fly.

Thank you for your attention – please leave a comment below if you feel it’s appropriate.


A32 Vixxen ferry flight to Queensland

Jeremy Hill with his new A32 Vixxen aeroplane

Here’s a short video about an aircraft ferry trip from Tyabb Airfield in southern Victoria to a cattle station near Dirranbandi in Queensland – a distance of over 650 nautical miles.

And here’s a bit of background. What turned out to be one of our favourite Aeroprakt A32 Vixxen aircraft arrived at Moorabbin in mid-December. I say ‘favourite’ because its new owner had chosen a great colour scheme, perfect for this time of the year – red wings and stabiliser with a white fuselage, fin and rudder, finished off nicely with a red propeller spinner. Our engineering colleagues immediately named it ‘Rudolf’ after Santa’s reindeer saviour.

Rudolf’s new owner – Jeremy Hill, based near Dirranbandi in Queensland – could not clear work commitments enough to come to us and pick up his new aeroplane, so my colleague and friend, Ido Segev, agreed to ferry it north. In all, the flight was over 7 hours’ in duration, plus stops, squeezed in before New Year, so Ido could enjoy celebrations with his loved ones on his return.

Departure day – 27 December – dawned clear but cool at Tyabb, with a strong northerly blowing – not ideal for a long trip northwards. Even in the A32 Vixxen, Ido was planning a ground speed of only 85 knots for the first part of his journey. Temperatures were forecast to be close to 40 celsius by the time he reached Jeremy’s farm, with the northerlies gusting all the way.

In the event, with a true airspeed around 115 knots and a ground speed of 95 knots, at around 7,500-8,500 feet, Ido made the journey in a single day, with plenty of daylight to spare. I suppose I could add that Rudolf was fitted with an autopilot, which helps a lot on long-distance flights. Nevertheless, it was still a long way over most of a day, in thermic and bumpy conditions.

Many thanks to Jeremy and his family for their hospitality during Ido’s visit and their 6-hour round trip by road to drop Ido at the nearest airport, so he could return home in time for New Year 2018!

The A22LS Foxbat – and more recently, its farmer-orientated sibling, the A22LS Kelpie – have been popular with outback owners for quite a few years. These rugged, easy to handle aircraft seem to stand up well to Australian country conditions. The icing on the owners’ cakes has been the excellent resale value when it comes to upgrade or switch to a newer aircraft.

It looks like the A32 Vixxen, with its extra turn of speed, is set to continue the Aeroprakt reputation for affordable aircraft with great (legal) load carrying capabilities!

As usual, to view the video, either click on the photo above or here:
Ido’s Vixxen adventure

Aeroprakt A32 crosswind at Tyabb

Crosswind at TyabbYesterday there was a fairly strong and gusty crosswind on Tyabb’s 35/17 runway. The crosswind was made even more tricky as the wind was blowing from the north west over the hills and trees near the airfield, making for very uneven and turbulent conditions.

Quite by chance, Mike Rudd, our video producer, was there trying out a new video camera, capturing a couple of aircraft landing – but due to the conditions, there weren’t many up and about in the skies! However, my colleague Ido Segev was flying an A32 Vixxen demonstration with a prospective owner. (Thanks to Stuart for the loan of his aircraft).

This very short video (click the photo or here to view on YouTube) first shows a landing by a Beech Travelair twin, piloted as it turns out, by Roger Merridew, a very experienced pilot and owner of Lilydale Airfield. He is followed closely by Ido and his passenger (who was sitting in the left seat) in the A32 Vixxen.

It’s interesting to note the different techniques used to land each aircraft in what was a 12-15 knot gusting crosswind. In many ways, as you can see, the A32 Vixxen handles the conditions better than the Travelair. The secret to making a successful crosswind landing in the A32 Vixxen is speed management and the minimal use of flap. The aircraft was down safely and exited at the first cross-taxiway, about 70-75 metres from the threshold of runway 35.

Good demonstration Ido!

PS – the prospective customer placed an order after the flight!

Icon A5 accident

The Icon A5 is probably one of the most hyped aircraft of recent years – a stylish, amphibious  Light Sport Aircraft carrying over US$85 million in investment over the last 10 years or so.

It uses the ubiquitous Rotax 912ULS (100hp) engine in a 2-seat pusher configuration and sports a highly designed automotive style cabin. All in all, it appears to be a beautiful and unusual aircraft – although at US$389,000, there will be a limited number of people who have enough pennies to buy one.

The only problem is that out of a total of 22 delivered aircraft (so far), three have crashed, killing three people, including a couple of senior employees of the Icon company.

Here is a link to a YouTube video which, I think, fairly and in an unemotional way describes the aircraft and the three accidents very well. It also makes some suggestions as to what may be the factors which have contributed to this extraordinarily high accident rate in what is probably one of the most tested new aircraft on the planet.

Click on the photo above or here for the video: Icon A5 accidents