LuvaraAir

My Feedback: (4)

I wouldn't call it "vastly improved" technology for auto engines. If it was so improved, that technology would be in airplane engines. Airplane engines are basic technology for one reason - it's simple, less stuff to break and that is what mitigates the safety risk.

Chris

Gravityisnotmyfriend

My Feedback: (2)

Yes, something like overhead cams would be more complicated but anything that is failing should be easily detected at an annual inspection. And there is no reason that any parts wouldn't last between major overhauls. I guess I can see your point about the simplicity, but can you explain the price?

iflyj3

My Feedback: (7)

Supply, demand, FAA certification and liability insurance.

Jimmbbo

That's it in a nutshell..

To some extent, it depends on what you want to do with the airplane... If your only plan is Saturday daytime hops in the local area, an automobile engine makes sense. If you plan to fly the airplane over some distances over inhospitable terrain or at night or IFR, I would use a certified airworthy aircraft engine and consider the price difference as insurance...

Granted, there are many good auto conversions, and they may have run well in the airplane, but they simply aren't designed for the 3D stresses of the aviaton enviornment. You don't know when one of the parts is gonna depart close formation, go walkabout and trash the engine, at which time I'd rather not be in the goo hoping I'll be able to see the ground when I pop out the bottom of the clouds... FWIW, the NTSB lists five RV-7/RV-7A accidents, four of which were pilot induced (three involved misjudged flare on landing... Hmm... an obvious emphasis area during flight training, I hope). This was the only one that was caused by a failure of the airplane:

NTSB Identification: CHI04LA011.
Aircraft: Domeier RV-7A, registration: N707DD
Injuries: 1 Minor.

The airplane was substantially damaged when it nosed over during a forced landing following a complete loss of engine power... The airplane was powered by a Subaru automobile engine converted for aircraft use. A postaccident examination revealed that the plastic timing-belt cover and the belts for the alternator and supercharger were broken. Pieces of the alternator belt were found within the remaining portion of the timing-belt cover. The engine intake and exhaust valves had struck the top of the cylinders.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The failure of the supercharger and alternator drive belts which resulted in foreign object damage to the valve timing system and subsequent loss of engine power...

Suggest a trip over to the EAA website http://eaa.org/ to get more information from experts in the field.

Cheers!

Jim

Jimmbbo

Chris,

I suspect most designers would give up their pocket protectors for the electronic engine controls and the fuel injection found on a standard Honda Accord instead of the magnetoes and float carbs or continuous flow injection on most GA airplanes... the electronic answer would be so much cheaper to produce, lighter, and more efficient... However.... Certifying a new engine is a very lengthy, expensive process, so the cost of certification of a new engine for a relatively small market keeps most manufacturers with the "tried and true" -

Since the price of "old tech" engines is already pretty steep due to product liability and the ever decreasing market (also due to run-amok lawsuits), the costs of certifying such an engine (which must be passed on, making the engine more expensive yet) just can't be justified...

Cheers!

Jim

Jimmbbo

Divorce sale??

Jimmbbo

Ben,

You got a keeper!!

Sport_Pilot

Ahh comon! You have never owned an airplane. Aircraft engines are vastly inferior to automobile engines. Their valves get stuck, the magnetos must be repaired every annual and replaced or overhauled every 300 to 500 hours. The magnetos on one plane I had were exactly like the one on my grandfathers tractor! No electronic ignition here. Cylinders have to be replaced, carb float's sink, the injection systems regularly flood the engine on startup. Made well but only if you compare it to 1940's quality! The bottom end is stronger than a car, but then they are built for lower RPM and higher torque, plus the precession of the prop. Most auto engines need a speed reducer of some sort and that should take the prop precession load as well. Properly inspected belts should not be a problem. I haven't had so much as a water pump or airconditioner belt go out on my car's in 20 years or more. Never had a timing belt go out. It's not like airplanes are without belts either. Plastic covers are not a problem either, in fact it would appear the Subaru cover that someone posted about was broke due to the broken belt inside. If you inspect every annual and replace accordingly there shouldn't be a problem.

Sport_Pilot

Although they exist, most of the lawsuits are fair and reasonable when you consider the junk GA produces. Airplanes that burst in flames when the wing tip hits a hanger during taxi, Bonanza tails that fall off in the sky, wings that fold up, etc.

Flyfalcons

Yeah but you don't run your car at 65% power for hours on end either. Car engines simply aren't designed to be run as hard as aircraft engines. If/when I build a plane that stalls faster than 30mph, it's getting an aircraft engine.

Rv7garage

My Feedback: (10)

Agreement with FlyFalcons- Mine will be FADEC, though.

Sport_Pilot

Another myth. Car engines run faster and hotter than an airplane engine. Their only real drawback is that the higer revs result in lower TBO, and weight. Cars normally run about the same revs around town and run harder than aircraft engines on the freeway. They can often do that till TBO without as much as changing the spark plug. I have had several cars which had no more maintenance than replacement of filters and cleaning of the original plugs. Aircraft plugs are lucky to last one annual because of all the crappy lead in them. Even the wires seem to go out soon, though partly because they are shielded.

Flyfalcons

How is what I said a myth? Car engines in cars may run at a higher RPM range but it doesn't mean they are running harder at all. Anyone who has flown a CS prop understands that. How often do you floor your car engine, let alone leave the pedal mashed for 5-10 minutes (average climb time on a short-medium length flight)? Based on fuel consumption, if your car is burning roughly 3gph on the highway (60 mph at 20 mi/gallon), then you are producing somewhere in the range of 30 hp. Not much of a load on a car engine that is rated for 160 horsepower. A 172 in cruise, burning 10gph, is producing around 100 of its rated 160 hp, and it will happily do it for hours on end. An engineer friend of mine taught me the 1gph = 10hp trick, and it is fairly accurate on all of the piston aircraft engines I have run when looking at power % and fuel burn charts.

As for the leaded fuel, more aircaft engines are being certified to run on auto fuel. I've flown a 182 with the STC, and it ran well, though a little cold-blooded on startup if the temperatures are low. I don't own the plane so I don't know how long the plugs are lasting.

Jimmbbo

Hmm.. I disagree that car engines run hotter and faster.... Let's compare a 160 HP airplane with a similar car on a cross-country trip....

Normal cruise power in light airplanes is 65-75% of rated HP - Take Flyfalcon's sample 160 HP Cessna 172 - that equates to 120 HP at 75%. The airplane will probably cruise at around 130 mph true airspeed. The block hour fuel consumption will be around 10 gph...

In my 160 HP Honda, I get around 25 mpg, using probably 40 hp and cruising at 65 mph for a block hour fuel consumption of 2.6 GPH

So, double the speed, four times the fuel consumption... Why the discrepancy? The airplane has to overcome more drag, requiring more HP and more fuel (Since drag increases as the square of the speed - double the speed, quadruple the drag, quadruple the HP required and quadruple the fuel flow (not entirely accurate, but close enough for our purposes)) Don't understand how a car is running hotter and faster when it is running at a fraction (25%) or the same rated power while the airplane engine is chugging away at 75% [sm=confused.gif]

While I agree that the technology of modern automobile engines is decades (literally) ahead of purpose-designed airplane engines, and I would love to see it implemented for the benefit of GA airplanes, the bottom line is that car engines are designed to be run in cars, under varying loads, but not at high power settings for extended periods of time. Airplane engines are designed specfically for high power usage for those extended periods, and until someone can get the cost of certifying those features under control, we're stuck with the old technology, and I could not recommend a non-aircraft engine for anyone contemplating using a homebuilt for other than local flying..

Jimmbbo

'taint true, m'friend... (emphasis added)

Until recently, property and liability insurance was a small cost of doing business. But the substantial expansion in what legally constitutes liability over the past thirty years has greatly increased the cost of liability insurance for personal injuries. For U.S. producers of private aircraft, liability insurance expenses now average $100,000 per plane produced, leading Cessna to cease production and Beech Aircraft to all but eliminate private aircraft production as well. These substantial costs arise because accident victims or their survivors sue aircraft companies in 90 percent of all crashes, even though pilot error is responsible for 85 percent of all accidents. http://www.econlib.org/LIBRARY/Enc/Liability.html

Sue-happy accident victims and willing lawyers have all but destroyed general aviation production by attacking the perceived "deep pockets" of any company or individual associated with aviation... I have consulted on several such cases including an Aero Commader 580 pilot who mis-flew an instrument approach and buried the airplane into the side of a mountain, killing three. Suddenly his surviors are suing anyone that ever had anything do with the airplane... In this case, the lawyer loaded the multi million dollar lawsuit shotgun and filed against Aero Commander (actually Rockwell, who bought the Aero Commander name - the 580 was out of production), Lycoming, Slick, instrument, avionics, pitot tube and chart manufacturers, mechanics and flight instructors (and this is but a partial list). The NTSB determined the probable cause as "pilot failed to maintain altitude awareness", but the costs of defending these "fair and reasonable" lawsuits was extreme and unnecessary, especially for the small FBO that maintained the airplane and the free-lance CFII who signed off the pilot's last Instrument Competency Check. Sadly, such post-accident activity is the norm rather than the exception... For the life of me, can't figure out how this is "fair and reasonable"... Seems more like "greedy and opportunistic".

I am unfamiliar with the situations where wings are bursting into flame or falling off, but it sounds like "the sky is falling" to me.. The Bonanza tail problem has been identified and remedied, and are the longest production GA airplane in history. I also disagree with your statement that GA airplanes are "junk"... A quick look at a GA ramp reveals that we have many 30, 40 and 50+ year old airplanes that are still flying safely. If they were all junk, we would see NO airplanes parked there, since lawsuits have killed new production...

Sport_Pilot

Statistics show that only skydiving and mountain climbing is less safe than IFR in a GA plane. And motorcyles are just barely less safe than a GA aircraft flying VFR. Those aircraft are not flying safely in my book. And after owning an aircraft and being around them a great part of my live, they are in many respects junk. If you compare them today and not 1950. You don't see cars with stuck valves. You don't see cars with ignitions systems that have to be replaced several times before overhaul. You don't see cars with poor engine efficiency. You don's see cars with fuel systems running through the cockpit. You don't see cars with seat belts that snap at 10G.

That was a Cressna 210 that burned the occupants to death after hitting a wing into an obsturction at slow taxi speed. As with most highwing aircraft the fuel lines run through the cockpit, seperated by only the headliner and panals. The wing bent back and pulled on the fuel line and cracked it spilling fuel over the occupants, a spark ignited the fuel, and toasted the occupants. They fixed the fuel system by putting self sealing fuel couplings between the wing and fuse. But that doesn't mean it couldn't happen to other high wing aircraft.

As far as product liability lawsuits, every manufacture has them. But the ones that make unsafe products or are not well healed enough go out of business. That is why Piper and other manufactures went out of business untill traded to a well healed owner. Because at least the smaller GA aircraft are unsafe.

Sport_Pilot

Poor comparison. First you are using rated horsepower not size. The aircraft engine is probably 2 1/2 times larger, and is rated at a much lower horsepower than its capablilities. Aircraft engines running gen sets run at higher speeds, same engine but maybe one less plug per cylinder and it is running a constant 3600 rpm for about half the TBO or 1000 to 1200 hours. (some actually do better because of the cooling fans, no hot running waiting to be cleared for takeoff). Why GA doesn't put powerd fans for cooling during taxi is beyond me. Your Honda is loafing, but similar engines run at or near full power in Germany on the autobaun and get the same or better TBO. Why? Because running at speed is actually less wear and tear than many starts, and stop and go driving. The aircraft engines run at much less than their capabilites and do not have to contend with short runs with lots of stop and go running, and do not have as many starts during their life. Consider that the caussut racers ran their C O-200's with smaller props than the C 150 and turned them at up to 4,000 RPM with few problems. Though I doubt they ran 100 LL thus suffering stuck valves every 10th flight or so.

ShoestringRacer

here is some good reading about engines. this is good evidence that what is best, diesel and rotary powerplants, are not always what is available. good info on automotive engine applications to airplanes and why it isn't so simple.

http://www.flyingmag.com/article.asp...article_id=501

http://www.rotaryeng.net/PeterGarrisonRotary2.txt

http://www.rotaryeng.net/P-Garrison-fly-art.txt

west6008

Homebuilts are dangerous, very dangerous.

To your mental health due to a stress level off the Richter scale.
I saw a grown man cry after nosing his Pietenpol over on its test flight.

To your marriage. Its too easy to become a recluse and social leper.

When I took flying lessons, I was shocked at the responibility and stress level
compared to model flying. Wake turbulence from a DC-9 did the trick for me!

I've known homebuilders in the 60's who were actually frustrated model builders.
Now, thanks to advanced and cheap RC, these type of guys are happy, and ALIVE.

Sport_Pilot

This is an exaggeration. For one you can use there is not that much flex in the propeller even metal ones. Wood propellers have almost no flex. Cars do not need torque converters to absorb shock. They have driven them directly with manual transmissions for years. Besides the propeller moves air which is less much less shock then popping the clutch in a car.

BOLTMAN

My Feedback: (1)

To get back to the original question, "How safe are homebuilt planes?"

Quote this to your wife to be, & it is a FACT.

More people are killed each year by donkey's than by light aircraft.

I own a factory build light sports aircraft that is available in kit form in some countries. I feel heaps safer when flying somewhere than travelling on some highway with all the loonies around. Especially during holiday times when traffic is usually much worse.

Good luck convincing your other half.

Cheers.

Rv7garage

My Feedback: (10)

wantsaneagle- good links, thanks.


west6008- I'm sorry that flying full scale was such a bad experience for you! At least you're still flying models. For me, nothing in full-scale aviation can be as purely frightening as the way people drive! The unpredictability of your average-IQ-of-100 driver is why I'd rather be in the air any day.

Sport_Pilot

Maybe I don't know. But I do know that the accident rate of motercycles is less than that of all GA aircraft. I also know that the worst part of it is IFR. VFR is saver than a motorcycle but still more dangerous than a car. Less injuries, but more fatalities. I posted a link to the statistics on a past thread, I'll have to find it and get back.

APIA

In regards to post #45, you have obviously never observed a propeller at speed with with the effects of a strobe light, this will get your attention in a hurry. Both metal and wood propellers flex quite a bit depending on the load. If they did not flex, you wouldn't have to worry about nicks and such...
Airplane engines, properly used and maintained, will usually provide thousands of trouble free hours. The main reason for engine failures, cylinder problems and ignition problems is either the lack of "proper" maintenance or human error. Letting airplanes sit in the hangar only amplifies maintenance problems.
As far as experimental airplanes go, during the building process, Big Brother (The FAA) performs stage checks as to the progress and quality of work performed. The FAA performs a final inspection before flight and after the hours are accrued you are issued an Experimental Certificate.
The RV-7 can be converted from "training wheels" to conventional gear by simply changing out the engine mount. I currently have a conventional version in my shop that I am finishing up for a guy. I has the good old "bullet proof" 160 Lycoming

Jimmbbo

Am looking forward to a source... find it hard to believe, knowing the number of friends who have been injured dumping their bikes...