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Comment by snarfy | Hacker News Reader

Why would there be a problem with the main engine? It seems like you should fix/redesign/etc that instead of adding another engine.

It reminds me of code that catches all exceptions instead of fixing the problem so those exceptions can never happen.

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Systems with moving parts undergo lots of stress. At some point, they will fail. Regular maintenance limits this; and the maintenance prescribed even for light aircraft keeps it to a minimum.

Still, no system is ever 100% reliable. The typical safeguard for engine failure in light aicraft is to glide to a safe landing. Starting with basic training, you'll do so repeatedly (starting from the vicinity of a landing strip, of course) and should be able to bring a plane down safely. Some (very) light planes even include a parachute system that'll bring down the plane in a manner safe for its occupants.

Speaking as a private pilot with little experience, this systems seems promising to me in two respects: In the case of a failed engine, it'll take you another 20 km or so. This can make the difference between a survivable landing in a field somewhere and a completely safe landing on the closest airstrip. Additionally, you get 40 hp or so of available power in situations where you need it, like taking off or going around after a botched landing. This could allow for shorter runways and help speed your initial climb, which is generally considered one of the most dangerous phases of flight: At that point you are both flying slow and low, and both speed and altitude are important safety aids. After a cursory first look, this system appears to be a considerable improvement in safety while avoiding much of the complexities a true twin engine system would entail.

> After a cursory first look, this system appears to be a considerable improvement in safety while avoiding much of the complexities a true twin engine system would entail.

Right. It's a sort of asymmetric thrust, coaxial twin. Very unusual, and clever too.

Fuel exhaustion, starvation, fuel contaminants such as water, catastrophic failure of components that are operating under extreme heat and stress, carburetor icing caused by high humidity, engine component icing (pressure/temp sensors on turbine planes, air induction icing on piston power planes), bird strikes. Piston and turbine aircraft engines are phenomenally reliable but all the best minds and all of the money thrown at the problem over the past 112 years have not reached a 0% failure rate. Electric motors don't have the complexities of combustion engines which would be reassuring when flying a single engine airplane over water, in bad weather, or over a populated area. I think it's an awesome idea that could add a huge margin of safety relative to the cost.

Light aircraft engines are already _very_ reliable, you'll most likely spend a career flying without ever experiencing a failure. The most popular GA motor, the Lycoming O-360, has been in production for something like 60 years, and is pretty much "debugged" as far as engines go. Still, failures do happen (most often because of user error). You can switch to turboprops, and you'll get more reliability, but higher costs. You can switch to a multi-engine plane, but again costs are higher.

An electrical motor which can provide backup assistance without causing further single points of failure is a nice add-on if they can make it work (I'd be sceptical about trusting this thing without extensive testing.)

Thank you for the responses. This is why I appreciate HN over reddit. I get comments with my downvotes.

I'm not sure why you were down voted to begin with, it's a valid question seeing how old many of GA engine designs are and how reliable modern internal combustion engines are. There's tons of advances in engine technology that isn't ported to GA aircraft for a lot of reasons, the biggest I would say is cost of FAA compliance and the insurance liability of failures. If your car engine fails on the highway you can still come to a safe stop. It's an extremely unlikely thing to happen on a modern car, but it's still possible (e.g. a cable is loose and disconnects the ECU). If your aircraft engine stops (which is also extremely unlikely, given the amount of routine maintenance it goes through to be considered airworthy) in the wrong phase of flight you're going to crash and possibly die.

Every plane you fly in commercially has at least 2 extremely reliable engines, and each one is certified to be able to handle flying the entire plane safely for an extended period of time to make it back to an airport in case of failure. The certification is called ETOPS [1], if a plane has 90 minute ETOPS certification it cannot fly more than a 90 minute flight from an airport. This appears to be a low-cost method of having a couple of minutes of safe controlled flight in case of a failure, that difference can make the difference between life and death for a GA plane.

This reddit thread has some good responses as to why Honda (who probably produces more engines in a month than Lycoming has in decades) doesn't make GA engines:

https://www.reddit.com/r/aviation/comments/1lxlco/why_doesnt...

[1] https://en.wikipedia.org/wiki/ETOPS

Your analogy misses the point that a fallback mechanism is needed in the rare cases where something unexpected happens.

Even in cases where you have everything formally defined, you could still have some axiom not holding, or a transient hardware issue - a random bit flipping in memory for instance.

Putting simply, everything fails eventually, the question is not "if" but "when".

Redundancy is a well-accepted (at least in aeronautics) way of providing robustness. When designing onboard systems for aircraft, it is not unusual to have a function with a higher level of design assurance which is implemented by a set of similar devices with a lesser level using a majority vote.

See multi-version dissimilar software: https://en.wikipedia.org/wiki/N-version_programming

Furthermore most modern planes are designed to be able to fly with one engine inoperative, even those which have only two engines.

Even "heavy" aircraft like commercial transport jets, which are serviced and monitored much more closely than light ones, have engine problems quite frequently; look through these, for example:

http://avherald.com/

Mechanical devices which never fail don't exist.

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