Make it as easy as possible! But for whom?
Comparing powered-gliders with retractable engines, both turbos and self-launchers, there are 2 philosophies, which are directly opposite to each other.
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The engine unit should be built-up as easy as possible.
Something, that is not included, cannot fail.
The Pilot will most likely rather change a Bowden-cable himself than sending in a complex ECU for servicing. -
Operating the engine should be as easy as possible.
This does not work without any electric operated devices.
But this is tested, reliable, comfortable and, most of all, safe.
Considering these first arguments, there is not much to criticize. One of my teachers came up with the following slogan 45 years ago:
Not all great things are simple, but all simple things are great
I remembered this throughout the years. How nice it was, when I was able to fix the carburettor of my car in when I was a student. Try this today with electric fuel injection!
Nevertheless: This is not a reason why you would dismiss the electronic injection in your car?
And this brings forward the second group of arguments. These are easy to understand and will appear to everyone, but what do they mean exactly? The concept with the DG-DEI has been proved for over more than 20 years now, and no-one will negotiate the fact that it is reliable and comfortable, as there is nothing to think about like what is just happening beyond one. So, what is it about the so apparent increase in safety? It seems to me that this is being underestimated drastically:
The DG-400 has been the first very frequently built self-launch glider with retractable engine. 285 planes were built and still today, the DG-400 is liked among its owners.
Unfortunately, we had to realize that there has been a series of accidents with powered gliders. Flying with a retractable engine had been expected as especially safely, due to the non-existent risk of a non-airfield landing. Instead, a new type of accident was created, which could always be traced back to the following kind of situation:
The Pilot, flying through poor thermals or being in the final approach, realises that he will not be able to make it with the altitude he has got left. According to the manual, possible fields for a non-airfield landing should be looked out for in a least 500 metres/ 1700 ft and then he should either start the engine or fly a proper circuit to land on the chosen field.
Frequently, this procedure didnt take place! Instead, the pilot would fly on, hoping that the remaining altitude would suffice or bearing in mind that he has an engine which should start immediately. This would be carried out until the top of the trees would almost touch thee wings and it became clear that the engine was required instantly to prevent the worst case.
At this level of upcoming panic, the pilot would have to follow a series of defined steps:
Switch on the ignition, deploy the engine, pull the choke or alternatively use the primer, depending on the estimated engine temperature, throttle in correct position and press the starter at the right time – and during all this keep fly the plane very close to the ground, also in the correct flap position.
And what happened then?
Well, in general the engine started and the pilot was relieved.
The same happened to me a while ago and afterwards I blustered against my own carelessness.
But what if the pilot made something wrong? If he didnt use the choke or flooded the engine with the manual primer-pump? Unfortunately, it often happened that the pilot fiddled around with the DEI until the chosen field was out of sight or the top of the trees ripped the tail off.
Some fortunate Pilots could afterwards talk about their carelessness and we possibly had another plane in for service – others werent as lucky
Once, when I was at high altitude in Vinon, France, I was able to see a well-known glider pilot who was forced to make a non-airfield landing with his open-class glider in the Durance-Valley, although it was equipped with a turbo-engine. You should have heard him going on about why it was possible to press the starter button, despite the ignition was switched off!
Another friend of mine with a different type of glider could not talk about his accident afterwards..
Like I said; this typical situation then also involved the DG-400 in a series of bad accidents, although everyone would have expected different, since the cause non-airfield landing almost totally dropped out. The file that analysed the accident would often say Pilots mistake as the reason, but who would this help, other than the manufacturer and his product- third party liability insurance? And many of the recent engine control units offer even fewer plausibility-tests than the DG-400 had in her time.
These kinds of accidents have drastically reduced since the introduction of the DG-800B with the fully automatic engine control.
Concretely, this means that many material damages did not occur and in a purely statistic way – approximately 3 to 6 fatal accidents less happened than with the same number of conventionally equipped powered gliders.
(We, at DG, dont know of a single case where a DG-808C pilot did not get the engine to run due to a too late deployed engine!)
By your leave, dont you agree that the just said is a very dramatic statement?
And the crazy thing: These 3 to 6 pilots havent got an idea about the fact that they would have had from a statistic point of view – a very bad accident without the automatic engine control.Of course, to them, everything has functioned just fine over the past years, and even then when they were extremely close to the ground and finally deployed the engine
, so why worry about this?
Well-yes!…
DG-Flugzeugbau percept that the whole engine concept should be as easy as possible – for the pilot, and not necessarily for the manufacturer!
Let us point out:
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It is cool to have a system which works fully automatically and releases the pilot from unnecessary operation.
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It is comfortable and fun, to fully concentrate on flying.
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It also contributes a considerable factor of increased safety- you may find it cool or not.
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And if you are in doubt whether you should afford this additional safety of course it is not cheap in production – just ask your wife/ your companion / your kids!
I just got home from a friend of mine who manages a research laboratory, developing new concepts for a well-known car manufacturer.
I asked him and his engineers how they sell their safety since in car industry- as opposed to the glider industry- safety obviously sells itself very well.
Do you know, based on statistics, if your cars are involved in fewer accidents with casualties than your competitors cars? And how do you deal with the results?
Answer:
We do have exact statistics, saying that a passenger with a fastened seatbelt has a chance of survival of almost 100% in an accident up to 100 km/h / 60 mph. This is not the case with cars of different manufacturers.
Naturally, we dont say: You will get killed if you buy a car from the manufacturer XY, but we do use these numbers offensively.
Most of all, we try to bring out safety as cool. Everyone wants to be cool nowadays; hence, something cool will sell.
And again, we also try to appeal to the wives and family that it is worth investigating in safety- everyone catches on that!
So, now you see where the slogan from further above originates from.
And if you would like to know which laboratory I visited, write me an e-mail.
I do not want to publish this information directly, particularly since I drive a car from a different manufacturer. 
– friedel weber – Translation: Justus Schiedek-Jacht
Dear Mr. Weber,
I enjoyed your arguments concerning the “Simple for who” approach to retractable engines, although, may I say that I believe the concept should be applied to all powered gliders.
I have frightening memories of trying to manage an IS-28 M2 with 65 hp on a typical Australian day of 35+ degrees! Even getting the thing off the ground, trying to manage fuel supply, boost pumps, engine temperatures, cowl flaps, propeller, retractable undercarriage with huge drag, etc left one with not much capacity left for the actual flying of the aircraft.
A recent training exercise in an H-36 Dimona reinforced this problem when the engine failed to start following a poorly planned approach which became very low. The trainee unsuccessfully attempted a re-start with a very cold engine. Fortunately my ‘Plan-B” was already in place and the aircraft was landed safely in a pre selected emergency area. That trainee learned a valuable lesson that day! Nonetheless, had the engine been managed by a capable electronic system requiring a simple one step start up operation that pilot could have been saved considerable risk, even if his landing area selection had proved unusable.
I therefore support your “Simple for the Pilot” philosophy, especially in the case of retractable self launchers and sustainers. However, coupled with that I believe it is important that a proper understanding of the built in systems is important, as should a failure occur, a pilot needs to clearly know what his alternative actions should be, what he can accomplish under emergency systems and more importantly what he cannot.
I am also interested to know what car manufacturer you referred to concerning the seat belt survivability rate.
Kind regards,
John G Viney
Senior Technical Officer, Airworthiness
GLIDING FEDERATION of AUSTRALIA
Tony Noble
Interesting article on whether simple is safer/better than complex with regard to Turbos or self-launchers.
I fly a Duo Discus T, so this discussion is close to my heart.
On more than one occasion I have sat watching the ground coming up to meet me while the Turbo propellor windmilled without firing. Each time, I either realised I had forgotten to switch on the ignition, or my flying partner in the back seat pointed it out.
Despite what we all know about best safety practice, everyone leaves deploying the engine until the last minute. The reason is that we are all glider pilots, and using the engine is an admission of defeat. In our Duo syndicate, using the engine is known as “The Burn Of Shame”.
My point is that an automated solid state electronic system is far less likely to fail than a human trying to remember a sequence of actions under stress. Glider engine systems should have two switches – one for on and one for off.
Regards,
T.