A32 Vixxen door latches – safety bulletin

Aeroprakt has issued a safety bulletin covering the door latches on A32 Vixxen aircraft, serial numbers 02-28. Compliance with this bulletin is required before the next flight of the aircraft.

Click here or on the drawing above for a copy of the bulletin: SA-A32-03 Door Latches

Rotax 912 series oil filter – new service bulletin

Rotax has issued a new mandatory service bulletin covering their oil filters – SB-912-071.

Due to a manufacturing deviation, the sealer gasket on the oil filter may leak, causing possible loss of oil pressure and oil.

If your 912ULS engine number is within the series from S/N 9 569 542 up to S/N 9 569 782 inclusive, or you have service replaced your oil filter since June 2017, you need to check the filter. If it has a green mark in the specified location, the filter is OK. If not, check for leakage and if any is seen, the filter must be replaced immediately. Even if there is no visible leak, the filter must also be replaced immediately on listed engines.

If there is no green mark on the filter, no leakage and the engine is not listed, the filter should be replaced within 25 engine running hours or within 200 days from 01 November 2017, whichever occurs sooner.

Here is a link to the service bulletin which gives full details: SB-912-071
Here is a link to the listed 912UL & 912ULS engines affected: SB-912-071UL

Urgent Rotax safety bulletin

Rotax has issued an urgent and mandatory service bulletin on their 912/914 series engines. It applies to a limited selection of engines built between June 2016 and October 2017 – check your Foxbat/Vixxen 912ULS engine number against the list below to see if you are affected.

(A) from S/N 6 785 971 up to S/N 6 786 198 inclusive
(B) from S/N 6 786 501 up to S/N 6 787 000 inclusive
(C) from S/N 9 569 001 up to S/N 9 569 690 inclusive
(D) from S/N 9 569 693 up to S/N 9 569 702 inclusive
PLUS S/N 9 569 823

In summary
Rotax reports that deviations in the manufacturing process of the valve push-rod assembly may cause partial wear on the rocker arm ball socket. This wear could lead to a rocker arm cracking/fracture which in consequence may lead to a malfunction of the valve train. Possible effects are rough engine running or an unusual engine operating behaviour.

The bulletin requires the removal of the rocker covers of affected engines and an inspection – and if needed, replacement – of the valve pushrods.

In simple terms, if the pushrod ends are a silver-ish colour, they are OK. If they are black they will need to be replaced.

Time frame for completion of the bulletin is:
– either at the next scheduled service
– or if a scheduled service is not due, within the next 25 hours of engine running time
– or if 25 hours running time is not completed, by 30 April 2018 at the latest

Here are links to the Bulletins:
What needs to be done: https://legacy.rotaxowner.com/si_tb_info/serviceb/sb-912-070.pdf
Which engines are affected: https://legacy.rotaxowner.com/si_tb_info/serviceb/sb-912-070ul.pdf

If you believe your engine is affected, please contact Bert Flood Imports, the Australia Rotax engine agent, for more information.
Bert Flood Imports phone number is: 03 9735 5655

Tie-down rings for A22LS & A32 aircraft

With Aeroprakt factory approval, we have developed a kit of tie-down attachments for A22LS and A32 aircraft. This is available as a retro-fit kit or as an installed option on new aircraft.

The kit consists of all the parts you need to add a tie-down point to the top end of each wing-strut and to the tail of the aircraft. There are full fitting instructions and also a copy of the factory Letter of Approval, which you’ll need, to keep the aircraft legally an S-LSA. Please note – non-approved changes to LSA planes mean they revert to ‘Experimental’ LSA – meaning you cannot use them for flight training and/or hire.

The photo here shows one of the strut rings but click here to take you to the Foxbat photo gallery where there are some bigger, higher resolution photos.

We are also developing a nose wheel tie down plate for use if you have to park your aircraft outside for more than a night or two – watch this space!

Cost of the retro-fit tie-down rings kit is A$295 including GST and postage inside Australia. As a fitted option on new aircraft, the price is A$335 including GST.

NB: this kit is not suitable for A22L aircraft.

Please contact Foxbat Australia at info@foxbat.com.au if you wish to order a kit.



Aeroprakt A22/A32 Weight & Balance calculator – update

UPDATE – by popular demand, the Weight & Balance calculators now enable fuel to be entered in litres – the calculator will work out the fuel weight and give you a gross weight and CofG as before. Hope you find that more useful.

We have developed a simple MS Excel spreadsheet to enable A22 and A32 owners to calculate easily their weight and balance before flight. For ease of use, all cells except the fuel volume in litres and weight values for the basic empty aircraft, pilot, passenger and baggage have been locked,

All you need to do is enter the fuel in litres and kilogram weight figures for your aircraft and the sheet will calculate your gross weight and the CofG position for you.
If all is within limits, the gross weight and CofG figures stay green. If they are outside limits, they turn red.

Please email me if you want a copy for your A22/A32Weight & Balance calculator – please specify if you want an A22L Foxbat, A22LS Foxbat, A22LS Kelpie or A32 Vixxen sheet as they are all slightly different.

Ballooning & floating?

Probably the most common comments I get from student pilots – and quite a few experienced pilots too – are about their perceived skills needed to land a light sport/recreational aircraft. In many cases, pilots make comments like: “I pulled back on the controls to flare and the aircraft just ballooned” or “it just seems to float and float along the runway; it just doesn’t want to land”.

Both of these events when landing an aircraft – ballooning and floating – have their own dangers for the pilot, which if not anticipated and handled correctly can result in a bent aeroplane…or worse.

So here are a few tips on how to get it right.

In simple terms, almost all balloons and floats during landing are caused by excess speed over the landing threshold. Unfortunately, many instructors have a habit of telling their students to add 5 or 10 knots to their approach speed ‘for safety’. In reality, in light sport aircraft in ‘normal’ conditions, they are often actually reducing the margin of landing safety by doing so. And this habit of adding speed to the book figure becomes instilled as a very hard-to-break habit. My own pilot training, now many many years ago, involved adding approach speed in certain circumstances and, even now, I have to fight the impulse to add speed when landing in the A22LS Foxbat and A32 Vixxen.

Let’s go ballooning
So, what’s wrong with more speed? There are two main reasons but first, remember light sport and recreational aircraft are very low weight (read: low inertia) aircraft. So, like a small car, these types of aircraft will change direction much more quickly than a limo, a ute or a truck. Not that I’m suggesting your average Cessna/Piper etc are trucks…. As a result, when landing, the controls are much more effective than bigger GA aircraft. At only slightly faster speeds the controls are even more powerful, so if you are too fast when you pull back to flare, the aircraft will not just flare, it will start to climb again, even with the engine at idle. This is called ‘ballooning’. When you go ballooning, the impulse is to push the nose down to reduce the sudden climb. Unless you are very quick (and/or experienced) you’re likely in for a bent nose leg and/or busted propeller. Another alternative, just holding back the controls during the balloon, can result in a stall from an ‘unsuitable’ height above the runway, leading to a (very) heavy landing, which could damage the landing gear or worse.

How about a bit of floating?
Next reason why too much speed is dangerous: even if you flare correctly without ballooning, the aircraft is still going too fast to land. Instructor: “Just try to skim the runway; don’t let the aircraft land; try to keep it flying as long as you can, slowly pulling back on the controls until the aircraft slows and the main wheels touch down”. This is all absolutely fine, unless you are carrying excess speed, in which case you’ll end up flying a long way down the runway before you touch down. And skimming along the tarmac (or grass) at relatively slow speed for a few hundred meters at just a few feet of height is tricky enough for an experienced pilot, let alone a novice. Throw in some cross wind, and/or a gust or two, and the risk of disaster rises exponentially! After a period of ‘skimming’ without landing, there is a huge temptation to let the nose drop a bit (or worse, push it down), just to get the wheels on the runway, and this can have two potential results: (a) because you’re still going too fast, the nose wheel touches down first and you’ll bounce/balloon, or (b) the impact will bend the nose leg and maybe bust the prop – if you’re lucky.

There are remedies for both ballooning and floating after they start but the easiest solution is not to let them happen at all!

Calculating the correct threshold speed
Which is where we get back to speed. There’s a GA rule of thumb about landing speed over the threshold. This says you should aim for about 1.3 times stall speed in landing configuration. As an example, with a stall speed of 45 knots the aim is (technically) 58.5 knots over the threshold – which is usually rounded to 60 knots. With low-inertia light sport aircraft, which have lower landing speeds, it’s probably safer to go for about 1.75 times stall speed, as wind gusts can be a much higher proportion of approach speed. So, for a stall speed of 28 knots (A22LS Foxbat) the threshold speed should be about 49 knots – which is exactly what the pilot manual gives. Note – this is 20 KNOTS above the stall speed!! If you come in at 55-60 knots over the threshold, you are flying about twice as fast as the stall speed – no wonder the aircraft is difficult to land!

What a drag
There are big differences in drag between aircraft. And drag affects how quickly the aircraft slows down when you throttle back for landing. The more the drag, the quicker the aircraft will slow down and vice-versa. To some extent, high-drag aircraft are easier to land than their more slippery siblings. As you cut power and round out to land, they will slow down more quickly, so if you are a few knots over the correct speed, they will help you out by slowing quickly. However, the more slippery the aircraft, the more accurate you need to be with the threshold speed; this is because if you are faster than you should be, the speed will not wash off quickly and ballooning and floating become much more likely.

As a comparison, our A22LS Foxbat is much much draggier than the A32 Vixxen. This is clearly evidenced in the fuel economy and cruise speeds. While the book figures for landing threshold speeds are much the same at 49 knots, coming in at 55 knots in the Foxbat will still allow you a reasonably easy landing. Try it in the Vixxen and because of its low-drag airframe, you’ll probably do a lot more floating. Add yet another 5 knots ‘for safety’ and even the Foxbat will take a while to land and the Vixxen will take you all the way down the runway into the fence at the end.

Landing weight
There’s an important additional piece of information needed here – the landing weight of the aircraft. All manufacturers quote stall speeds at maximum gross weight – for light sport aircraft, this is 600 kgs. If the stall speed is 28 knots at 600 kgs, it will be noticeably slower at (eg) 450 kgs actual weight, which in an A22LS Foxbat equates to the aircraft with one pilot and 50 kgs (70 litres) of fuel. In fact, it could be as much as 3-4 knots slower. Re-calculating the approach speed for this weight: (eg) 25 kts x 1.75 = 44 kts.

Hopefully, instructors  teach their students properly about the difference weight can make to stall – and thus landing – speeds. This is particularly important for light sport aircraft, where the pilot, passengers, fuel and baggage make up a much bigger proportion of the weight and therefore have a much more significant effect on speeds than heavier GA aircraft.

Finally, a point about wind. I’ve often heard it said you should add 5-10 knots to your approach speed if the wind is across the runway and/or gusty. The idea being that if the wind suddenly drops during your approach, the aircraft is still going fast enough to keep flying above stall speed. In heavier GA aircraft, this may well be valid, as using the throttle to regain speed to arrest the momentum of a sudden descent takes time. However, modern light sport aircraft are much more responsive to throttle than their older GA counterparts, so I would never add more than 5 knots to the ‘book’ approach speed in a cross or gusty wind and use the throttle to stop descent quickly if a sudden drop occurs due to a gust.

In summary – read the pilot manual for your aircraft to check the threshold speed for that specific type – do not rely on rules of thumb, like “all aircraft are OK at 60 knots” down final and over the threshold. If the manual gives 49 knots at gross weight stick to it and – if it’s a light sport aircraft – even a bit slower if you do not have a passenger and/or lots of fuel. If you don’t stick to the book speeds, you are looking for trouble and for sure, you’ll end up ballooning or floating and sooner or later you’ll bend something. Hopefully, not yourself or your passenger!

KievProp propeller balancing

Here’s a great little video about how to statically balance your KievProp – ie off the aeroplane. I suppose the technique could be used for any type of propeller. It certainly works here!

As a matter of interest, you can also dynamically balance your propeller – ie when attached to the aeroplane, with the engine running. However, this does need a piece of electronic kit (which is not cheap and simple) which in principle works in much the same way as the static balancer.

Overall, for an inexpensive and excellent balancer, the static approach works well.

PS – be sure the carburettors are correctly balanced (ideally with the engine running) and the blade pitches are all exactly the same…not even a skerrick out!

As usual, click on the picture or the link to get you to the video.