Rotax Engines (4) scheduled maintenance update

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Over two years ago, I wrote a blog post about Rotax engine scheduled – ie regular – maintenance, like oil and filter changes and other time-based servicing.

At that time, I said that the information in the Rotax manuals was ‘about as clear as old engine oil’. After several emails around that time the Rotax-Owner website confirmed by email to me that scheduled maintenance times on 912 series engines should be by reference to flight times – ie ‘wheels off to wheels back on the runway’ – as required by FAA in the United States.

However… it turns out that this may have been wrong. Current Rotax manuals, updated in the last two years, apart from a couple of small anomalies, clearly state that scheduled maintenance must be according to engine start-up and shut down times, as recorded by a reliable engine hours timer. This is further supported by Aeroprakt – manufacturers of the A22LS Foxbat and A32 Vixxen aircraft – who have aligned their airframe maintenance times with those required by the engine manufacturer.

This comes as a blow to many flight schools operating aircraft with Rotax engines, who have serviced their aircraft based on flight times – just like, I may add, the vast majority of the Lycoming and Continental engined GA fleet. At larger airports in particular, start-up/shut-down times can be as much as 25% and more, longer than flight times. When allowing for engine warm-up on cool mornings, the overall % could be even higher – substantially increasing maintenance costs.

Nevertheless, as one of my Aeroprakt colleagues put it: ‘in all aircraft, vibration from engine running is one of the major factors affecting the airframe fatigue life’. This is particularly true of the recreational and light sport category, where airframes have to be constructed to lighter standards and closer tolerances than many GA aircraft. So the aircraft may be less expensive to buy but will require more frequent maintenance. Thankfully, overall running costs in recreational and light sport aircraft are still only a fraction of those in their heavier GA relatives.

So – make no mistake, if you have a 912-series Rotax engined aircraft, scheduled maintenance must be carried out based on engine running hours, NOT flight times!

A few lines of aviation humour

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What follows are a few lines of aviation humour to help you through your Monday morning. I’ve heard some before but not all of them.

Happy smiling!

  • There are more planes in the ocean than submarines in the sky
  • The only time you’ve got too much fuel is if you’re on fire
  • Flying is the second best thrill in the world – landing is the best
  • Death is just nature’s way of telling you to watch your airspeed
  • You can watch the clouds go by – or fly above them
  • An optimist invented the aeroplane, a pessimist invented the parachute
  • A helicopter – thousands of parts flying round an oil leak waiting for metal fatigue
  • The three most common aviation expressions: “Why is it doing that?”, “Where are we?” and “Oh crap”
  • Modern aerial warfare: a $70 million aeroplane drops a $350,000 bomb on a $10 tent
  • In thrust we trust
  • Engine power: lots is good, more is better, too much is almost enough
  • Pilots get paid to sit and stare out of the window
  • The emergency exit row – with great legroom comes great responsibility
  • When all else fails – use duct tape
  • When opening the overhead bins take care – shift happens
  • Loud, sudden noises in a helicopter WILL get your undivided attention
  • Latitude is where we got lost; lontitude is how long we’ve been lost
  • There are certain aircraft sounds that can only be heard at night or over water
  • No need for a checklist, I’ve got it all memorised
  • Mummy, when I grow up I want to be a pilot. Sweetie – you can’t do both
  • The flight attendant smile – fooling passengers since 1912

Carb icing or fuel vaporisation?

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Over the last year, I have received a couple of reports of what was described as ‘fuel vaporisation’ causing rough running in an aircraft with a Rotax 912 series engine.

Intrigued, as there have been no other mentions of ‘fuel vaporistaion’ – let alone actual confirmed reports – in the entire 1,000+ global Aeroprakt fleet, I decided to do some internet and personal investigation on fuel vaporisation and carburettor icing (something which can, in some circumstances, give similar symptoms). As a bit of background, we currently have close to 175 Aeroprakt aircraft operating across Australia, from the searing outback summer temperatures of 45+ celsius to the cooler temperatures of Tasmania in the winter. While occasional carb icing has been reported, never has fuel vaporisation been mentioned…until this last 6-9 months.

Here’s what I found about fuel vaporisation.

Vaporisation typically happens at high ambient temperatures – websites I viewed suggested at 35-40 celsius and above. However, the likelihood of  fuel vaporisation can be affected by a number of factors: mogas vaporises much more easily than avgas; fuel under suction (eg in the line from a tank lower than the pump) will vaporise more easily than fuel under positive pressure (eg in a line from a tank higher than the pump); carburettors without vent lines are more susceptible than those with vent lines like the Rotax engine. The most typical scenario for a vapour lock is when an aircraft with a hot engine after a flight is parked and the temperature in the fuel lines in the engine bay can soar well above 60 or 70 degrees celsius, causing the fuel to boil in the lines in the engine bay – making restarting difficult. In fact, Rotax recommends that for engine bay temperatures over 45 celsius, the fuel lines and carburettors should be ‘cooled’ although they don’t specify exactly how.

It is very unusual (but not impossible) for vaporisation to occur when the engine and fuel lines are relatively cool (eg during a descent) or when cruising or climbing at normal or higher power settings, when there is a good flow of cooling air over the engine and cooler fuel is flowing from the tank(s).

Here’s what I found about carburettor icing.

Carb icing typically but not exclusively occurs at slow cruise or low power/idle throttle settings. It can occur quickly and at surprisingly high temperatures – see the graph above. For example, on descent, there is a ‘serious’ risk of carb icing at temperatures as high as 30 celsius and as low as 35% humidity. Carburettor heat can help prevent icing but once formed, ice can take a while to clear. In fact, descent into warmer air is sometimes just as effective at clearing the ice – provided the engine is still actually running. As with vaporisation, mogas is much more susceptible to carb icing than avgas; fuel with ethanol and/or other additives can be more prone to icing, as the fuel may have absorbed water. Even with carburettor heat, I was trained to warm the engine on longer descents by applying 80%+ power for at least 30 seconds every 1,000 feet of descent – and that’s with avgas, which is much more resistant to icing than mogas.

So, what is the most likely cause of a rough running engine in the following circumstances: icing? Or vapour lock?

  • descending aircraft
  • low cruise power setting
  • ambient temperature around 22-25 celsius
  • relative humidity around 55-60%

After long discussions with the Aeroprakt factory covering the reports which have been made, it is our conclusion that the reports of ‘fuel vaporisation’ causing rough running may have been mistaken for simple carb icing, which is a much more common problem. The prevention of vapour locking and carburettor ice are quite different – a fuel/vapour return line for the former and carb heat for the latter. Although it must be stated clearly that neither solution is guaranteed to be effective in all circumstances.

Some early Aeroprakt aircraft were fitted with fuel return lines, although these have in the past caused problems of their own, with excess fuel pumped overboard due to wrong tank selection. Current ASTM standards for Light Sport Aircraft do not require an excess fuel/vapour return line to be fitted. The Rotax manual, although stating a return line is ‘mandatory’ in one place, actually states that the fuel system is ultimately the responsibility of the aircraft manufacturer. All Aeroprakt aircraft manufactured after February 2015 either have a fuel return line fitted or one can be retro-fitted by owners if required.

Retirement age for GA pilots?

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Here’s an interesting one – should there be a fixed retirement age for GA (ie light aircraft) private pilots?

Airline, military and other professional pilots have a mandatory retirement age of 65, sometimes younger. And even before retirement age, it is sometimes required that a co-pilot is mandatory and must be under the age of 60. But as such, there is no official retirement age for us recreational and sport pilots.

A recent study in USA (by Alpo Vuorio and others, published in Aerospace Medicine and Human Performance) looked at over 100 fatal accidents involving private pilots in the age range 70 to 92 years over a 10-year period. Pilots in this age range represent a relatively small percentage of the pilot population (around 7% on most recent figures).

The study looked at the possible contribution of anti-depressants and anti-histamines in fatal accidents.

It was found that anti-histamines were present in the blood of almost 20% of the pilots in this age range who died in aviation accidents. The study concluded that this may be because, in this age group, the sedative effects of anti-histamines may be used as sleep medication – but the problem is that anti-histamines reduce REM (‘rapid eye movement’) sleep and therefore may impair performance.

Anti-depressants were present in almost 10% of pilots who died in accidents. While there are anti-depressants which are suitable for use by pilots, there are plenty which are not, because of their negative side-effects, including fatigue, drowsiness and blurred vision. The study also noted that over 12% of fatal accident pilots had been taking three or more different drugs at the time of their fatal accident.

These findings are interesting in the light of the trend towards GP based (rather than Designated Aviation Medical Examiners – DAMEs) for GA and recreational medicals. On the one hand, it could be argued, GP medicals may not be as stringent as those by a DAME, on the other hand it is likely that a pilot’s GP will be more aware of medications which the pilot may be taking and their overall general health.

All this attention on medications should not divert attention from the inexorable process of ageing, which takes its toll on reaction times, physical strength, eyesight, hearing etc etc. Some older friends and colleagues of mine have decided to hang up their flying goggles after a near accident; others took the decision before it was made for them. Whatever our age, we should all fly within our capabilities and watch out for the occasional bounced landing which gradually, almost imperceptibly, becomes the norm. And we all read about Harrison Ford* (age 74) landing on a taxiway, over the top of a waiting airliner, even though he probably has more flying experience than most of us….

As some kind of a safety net, there is a 2-yearly compulsory Aircraft Flight Review (an AFR; used to be called a Bi-Annual Flight Review, or BFR) to at least identify potential pilot shortcomings and give advice on improvement – maybe the check instructor should be asking what medications the pilot has taken in the 48 hours before the review?

But overall, to reduce the chance of an accident, stay fit, sleep well, don’t fly if you’re under the weather(!), avoid anti-histamines and anti-depressants and read the side effects of any and all medications. If in doubt stay on the ground and don’t risk becoming a statistic….whatever your age!

* There is no intention here to suggest that Harrison Ford was taking any medication or any other drugs which may or may not have influenced his decision making

 

Australian Airshow 2017 – Avalon wrap

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Mike Rudd, in his own inimitable style, has produced an excellent short video covering the 2017 Avalon Airshow. Although majoring on the Foxbat Australia display, there are comments from Evektor Aircraft and Sling Aircraft, as well as a selection of interesting people who visited our static display.

As usual, click on the picture or use the following link to see the video: 2017 Avalon Wrap

A22LS Foxbat beach landing

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french-island-01This afternoon (25 February) an A22LS made a beach landing at the eastern tip of French Island, Victoria.

The news media has variously reported this as an ’emergency’ or ‘forced’ landing and that three people were on board. None of this is true and most outlets have now corrected their initial reports.

The pilot and a friend were taking the aircraft from Tyabb on a flight round the local area, when they decided to make an unplanned landing on a beach where they had seen other aircraft land in the past. Unfortunately, although they did a check fly past first, the sand (and some mud) turned out to be deeper and softer than they expected.

The aircraft landed safely but when turning to taxi for take-off, it became clear that the sand in places was very soft and they would not be able to take-off again. During entry into some soft sand, at only a slow taxiing speed, the propeller suffered damage to the tips. The pilot contacted the authorities to report the situation. No-one was injured (other than their pride!) in any way.

The aircraft has been moved up the beach to be well clear of the tide and will be retrieved by barge on Sunday before checks and any needed repairs are carried out for the aircraft to return to service.

There are lessons in this for all of us. Although the A22LS Foxbat has an enviable record, including many thousands of safe off-airport landings by farmers and station owners, you can never presume that landing areas remain the same today as yesterday. Wherever sand and water meet, there is always the possibility that the surface is not as solid as you thought.

Thankfully, this landing resulted in no more than some severely dented pride and only minor damage to the aircraft’s propeller.

 

AeroTV and Aeroprakt A22LS

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dennis-at-delandAero-News Network Inc has published a short review of the A22LS (Foxbat) on their YouTube channel AeroTV. Headlined ‘Versatile AND Practical – The All-Seeing Aeroprakt A-22 LSA’  AeroTV’s Tom Patton interviews Dennis Long, Aeroprakt’s USA dealer at the recent Deland Sport Aviation Showcase, held in Florida each year.

The video includes some rather old flying footage of an early Australian A22L, plus some newer video of a glider tug A22LS at Benalla in Victoria.  The report gives Dennis a great opportunity to describe the aircraft and its capabilities – which he does excellently! I must remember some of the phrases he uses to use myself at the upcoming Avalon Airshow. Particularly coming to mind are: “…just the best handling light sport on the field.” And: “…taking off on gravel or sand, it does a very fine job of that because the nose comes up right away and you’re balancing just like a taildragger.”

God job, Dennis!

A22LS Foxbat – ‘long leg’ option

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long-leg-panel-01Aeroprakt Limited has recently announced the availability of a factory-installed option of a revised instrument panel with cut-outs along the bottom edge to help accommodate those pilots and passengers with long legs – see photos.

Although I am 1.88 metres (6′ 2″ in imperial) tall, I have never found a problem with the leg room in either the A22 Foxbat or A32 Vixxen aircraft. However, a friend, who is exactly the same height as me, has often complained about the lack of knee room for him in the A22 Foxbat. Apparently, I have a longer body and shorter legs; he has a shorter body and longer legs – one reason I advise all potential aircraft buyers to actually sit in the aircraft on their shortlist, to check knee/leg room and head clearance. A particular height or body weight does not guarantee a comfortable fit even if an apparently identical size friend fits perfectly!

long-leg-panel-03Many thanks to Aeroprakt, therefore, for introducing this ‘long leg’ option on the A22 Foxbat. The pictures clearly show the panel cut-out modification, which is only available on stick control versions of the aircraft. As yet, this option is not available for the A32 Vixxen, neither is it easy or inexpensive to retro-fit to existing aircraft as there is a significant change to the instrument panel support structure.

AVweb flies the Aeroprakt A22LS

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avweb-dennisOur very own Dennis Long of Aeroprakt USA takes AVweb’s Geoff Rapoport for a flight in the A22LS at Sebring, Florida during the recent Sport Aircraft Expo.

Great video Dennis – not too sure about the colour scheme…

AVweb describes itself – rather modestly – as ‘the world’s premiere independent aviation news resource’ and they certainly have a wealth of interesting content and aircraft reviews. Have a browse.

One of my personal favourites is Paul Bertorelli’s rather sarcastic comment on the huge patterns – ‘circuits’ to us non-USA pilots – which instructors use when training. It’s one of my personal gripes at my home airfield, where sometimes club aircraft doing circuits seem to set out on scenic flights along the bay during the downwind leg. I was taught, admittedly by military instructors, to take-off, climb to 500 feet AGL, then make a turn and climb cross-wind to 1,000 feet AGL, then turn downwind. I fully accept that a Foxbat or Vixxen will get to these heights much quicker than a C150 or C172. However, even when I’m doing circuits in my relatively leisurely Interstate Cadet, the club Cessnas are usually way outside of me. It makes circuits a real chore as it’s very bad manners to cut inside. And, as Paul comments, it tends to train pilots to do long, straight in approaches, using engine to ‘drag’ the plane in to the threshold, which is not always possible in ‘real’ life.

As usual, either click the picture to take you to the A22LS video, or click here: AVweb flies the Aeroprakt A22LS

Aeroprakt A32 1,000 nm ferry flight

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ido-shaun-at-emeraldMy colleague Ido Segev and his friend Shaun just got home from an almost 1,000 nautical mile ferry flight of a new shiny Ferrari red Aeroprakt A32 Vixxen, registered VH-ACL, to its new owner Will Graham.

The aircraft is fitted with a Dynon SkyView system, including a 2-axis autopilot, transponder and fuel computer. In addition to the standard dual-watch VHF radio, the aircraft also has an 80-channel UHF radio, operating through the headsets.

ido-shaun-ferry-02Their flight took them from Moorabbin Airport, near Melbourne, via Temora and Parkes in New South Wales, to an overnight stop at St George in southern Queensland. Most of the flight was made at 8,500-9,500 feet AGL, which at times translated into a density altitude of over 11,000 feet. Said Ido: “Even at 7,500 feet were were still climbing in excess of 500 feet a minute – not bad with two of us, full fuel, luggage and some spare parts on board.” The next day, the weather wasn’t so kind, with strong headwinds and a 2,000 foot cloud base. Nevertheless they made good time and arrived at Emerald, Queensland, before lunch, after a short wait at Roma while some weather passed through.

Total flight distance was about 950 nautical miles with and average ground speed of slightly over 95 knots. Average fuel burn was a shade under 17 litres an hour. In metric fuel economy terms, that’s about 10.3 litres per 100 kilometres – not bad for an average speed of over 175 kilometres an hour! Ferrari and co, eat your hearts out!