RE: How safe are homebuilt planes?

RE: How safe are homebuilt planes?
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RE: How safe are homebuilt planes? - 8/24/2006 7:07:16 PM

Jimmbbo

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From: Fresno, CA, USA
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quote:

ORIGINAL: Sport_Pilot

quote:

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

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.

Thanks for proving my point... the airplane engine is designed for its operating environment - long duration at constant RPM, the auto engine for its ever changing speed, start and stop... Similar things that do different jobs... sorta like a plow horse and a quarter horse... both are horses, but I wouldn't expect a quarter horse to pull my plow for long...

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Post #: 51

RE: How safe are homebuilt planes? - 8/24/2006 7:16:45 PM

Sport_Pilot

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From: Acworth, GA, USA
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quote:

The main reason for engine failures, cylinder problems and ignition problems is either the lack of "proper" maintenance or human error.

The problem is that the maintenance requirments are huge. Because they are so antiquidated they don't enjoy the benifits of electronic ignition, computer controls, or unleaded fuel. The certification process is too expensive and restrictive. Because of this cars can go 50,000 miles or almost 1000 hours and usually much more without maintenance. Now I don't recommend this as a maintenance schedule, but I would say many if not most recieve no maintenance other than oil changes till it misses or quits. Aircraft on the other hand cannot go more than 300 hours without new points and plugs. Yes I know the plugs should be checked and the points replace every annual or 100 hours. But this fact also means the automobile ignition system is more reliable. The same goes for the fuel system. Even the oil is inferior, but that is because of the leaded fuel, detergent oil cannot be tolerated.

Wood propellers have very little flex, that is why the break instead of bending. Nicks have little to do with flexing. To boot the cars drive shafts and axles have similar flex, and are not dampened by air. As I said the flex is noting like sidestepping the clutch on a car, and most can take a fair amount of this abuse. That said there is a problem with many reduction drives, but much of this is due to the radial load and poor design.

< Message edited by Sport_Pilot -- 8/30/2006 6:44:07 PM >

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Post #: 52

RE: How safe are homebuilt planes? - 8/24/2006 7:20:59 PM

Sport_Pilot

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quote:

Thanks for proving my point... the airplane engine is designed for its operating environment - long duration at constant RPM, the auto engine for its ever changing speed, start and stop... Similar things that do different jobs... sorta like a plow horse and a quarter horse... both are horses, but I wouldn't expect a quarter horse to pull my plow for long...

Obviously you missed my point. If you took an automobile engine and ran it like an aircraft engine it would last longer than it does now. The larger automobile engines would last longer than the aircraft engine, the smaller ones about the same. This is due to their superior cooling system and unleaded fuel. If they just put cooling fans on the aircraft engines and closed up some tolerances they would probably be better than that.

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Post #: 53

RE: How safe are homebuilt planes? - 8/24/2006 7:35:28 PM

APIA

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What tolerances? Both types have virtually the same tolerances. That is if you are talking about internal tolerances..... I would like to see how long a car engine would last running at 75% for 2000 hours.... A nick in a propeller blade is where propeller blades break, (kind of like scoring glass to break it) I will look for the link that I saw that shows how much propeller blades flex in all flight regimes, both wood and metal.

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Post #: 54

RE: How safe are homebuilt planes? - 8/24/2006 8:18:13 PM

Sport_Pilot

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quote:

ORIGINAL: Jimmbbo

quote:

ORIGINAL: 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.

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

I couldn't get the info form Aviation Consumer as I no longer have a subscription. The article was over ten years old and I wonder if they would still have it on their site? Tempted to resubscribe. I hope to fly full scale again someday.

However I did google this up.

http://www.magma.ca/~ocbc/comparat.html

As I recall Aviation Consumer pegged all GA flying at about the same as this. But IFR flying was much worse, and VFR flying was between that of a motor cycle and a car. I recall that AC converted reported statistics to the same factor, passenger hours I believe. If converted to miles it puts GA in a better light. I see a "not invented here" attitude from the GA industry and FAA toward bringing some of the auto tech into GA aircraft. Surely they would benifit form electronic ignition, fuel injection, and computers. I think EPA would have to get involved to get them to rid leaded fuel.

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Post #: 55

RE: How safe are homebuilt planes? - 8/24/2006 8:23:30 PM

Sport_Pilot

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quote:

What tolerances? Both types have virtually the same tolerances.

I recall the ring gap and piston to cylinder gap is wider in aircraft due to running hot when sitting at the hold line. Or so it was explained to me by an old A&P mech. I could be wrong, but they seemed wide, but then again the cylinders are generally much larger. This from a conversation while helping him rebuild an aeroclub aircraft. He was a VW fanatic also, and he thought they should have some small fans for those occasions.

< Message edited by Sport_Pilot -- 8/24/2006 9:02:21 PM >

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Post #: 56

RE: How safe are homebuilt planes? - 8/24/2006 8:51:05 PM

Ed Toner

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I think the pilots of many of these homebuilts are low time types, and they constitute a large percentage of the accidents.

This reminds me of the Beech Bonanza, a very safe aircraft, the Cadilac of private aircraft. They became known as "Forked Tail Doctor Killers", because many MD's bought them. They had more money than piloting ability.

I know one personally. He told me he almost killed himself a few times so he sold his Bonanza and bought a yacht.

He lived happily ever after.

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Post #: 57

RE: How safe are homebuilt planes? - 8/24/2006 9:01:25 PM

Sport_Pilot

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quote:

This reminds me of the Beech Bonanza, a very safe aircraft, the Cadilac of private aircraft. They became known as "Forked Tail Doctor Killers", because many MD's bought them. They had more money than piloting ability.

Ahh, Beechcraft lost a lot of money when it was found that the tails were literally falling off. They also had to reinforce all of the existing aircraft with a cuff to keep the leading edge of the v tail from fluttering.

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RE: How safe are homebuilt planes? - 8/24/2006 9:03:49 PM

APIA

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The Good old "V" tail Bonanza has killed many folks, Some pull the wings off of them, or tail, usually by exceeding the aircrafts limitations. This is a nice airplane that can do a lot of things well, however, It is not an invincible aircraft. The other one I continue to see is loss of control due to tail heavy conditions. The fuel cells on this model are forward of the CG, loading the airplane without this consideration will ultimately be a hand full or uncontrollable. It might be balanced when you leave but will be a surprise at your destination. Some of the older Bonanzas had a very complex fuel system, if the system is not understood this usually ends up in the fuel starvation column.

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RE: How safe are homebuilt planes? - 8/24/2006 9:20:39 PM

Sport_Pilot

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quote:

This is a nice airplane that can do a lot of things well, however, It is not an invincible aircraft.

Yet somehow it has a poor safety record. Yet somehow the t tail version and those which had the tail cuff AD performed on them have a good safety record. Yet the same people are flying them. Face it aircraft are dangerous, some more than others. Yes training can help you to beat the statistics, but those same people are likely also beating the automobile safety statistics.

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RE: How safe are homebuilt planes? - 8/24/2006 9:36:03 PM

Ed Toner

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Thanks for enlightening me on this matter. I had no idea. I am not a light plane pilot. To me, the B-727 was a light plane.

I retired on the L-1011 in 1987.

The last "craft" I flew was the Paraplane. That was pure fun, and safe. I leased them by the hour. Tom Snyder was the designer and manufacturer. I heard he bought the farm in a warbird, ran out of fuel.

I noticed a lot of his demo's took off with less than a full tank. I always insisted my tanks were topped off to full.

I've accumulated close to 20,000 hours over my 34 years of flying, never an accident. Though I never blew a tire flying Banshee's off the WASP, I blew one on a B-727 landing on standing water at CLE. Hydroplaned, turned off the anti-skid to stop. No NOTAM or warning from the tower.

http://www.airdisaster.com/user-uploads/its_smoke.gif

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Post #: 61

RE: How safe are homebuilt planes? - 8/24/2006 10:02:11 PM

Sport_Pilot

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From: Acworth, GA, USA
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quote:

That was pure fun, and safe.

LOL, well reasonably so. IMO the worst problem with GA is IFR flying. The rules and instruments are too complex for those who are not staying proficient (and too many do not), and too many planes flown IFR just do not have enough performance to be safe when caught in bad weather. IMO any airplane that cannot climb 1500 or so FPM and do not have two alternators should be VFR only.

BTW - The flying doctor theory was started by Beechcraft, at least according to some lawers. Finally somebody in the FAA got smart and simulated the V tail on a shaker in a wind tunnel to find the problem, the leading edge of the tail was not secured to the fuse, the ribs were simply attached to the spar and only the spar was attached to the fuse. When it failed the leading edge would flap up and down until it failed, the down (or up) force from the failure often broke the tail cone off! Lawers used the flying doctor theory against Beechcraft to great success convincing juries that they knew about this, which is why they came out with the t tail version (the Debonaire?). I don't know if this is true or not, but I guess the juries thought it was. I think it alsmost put Beechcraft under till bought by Rayathon.

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RE: How safe are homebuilt planes? - 8/24/2006 10:19:30 PM

Ed Toner

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I spent 3 years instructing in the T-34 at NAAS Saufley, 1959-1962. That was a Beechcraft, too, but it could really take punishment.

One structural failure caused one half the stab/elevator to fall off. The instructor landed it safely. I had the task of helping the Beech engineers find the cause. It was because of pressures during steep turn stalls during cruising configuration and excessive "G"s.

This caused buffeting on the stab., that eventually caused the failure.

< Message edited by Ed Toner -- 8/25/2006 1:01:55 AM >

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RE: How safe are homebuilt planes? - 8/24/2006 11:33:51 PM

west6008

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From: Morell, PE, CANADA
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I think that private pilots should routinely practice full deadstick landings.

If you go to the NTSB aviation website

http://www.ntsb.gov/ntsb/month.asp

You'll be amazed at the botched forced landings
where people hurt themselves in light planes that
have good glide ratios.

I taught my son RC flying at age six, and like all of us, made hundreds of forced
landings with models.
Now he has a Commercial license, and I hope if he is faced with a forced landing that his RC experience will help.

(in reply to Ed Toner)