170 glide ratio

russfarris · Post by **russfarris** » Mon Nov 29, 2004 5:02 am

I did a search here on the site and a Google search on this. One source claims the glide ratio of the stock 170B is 7:1; with their STOL kit and VGs, they claim 13:1! (I forget which company it was, I'll look it up later.) As an old sailplane pilot, I find that kind of improvement highly suspect at best.

The 172 comes up as being around 9:1, which seems about right for a 170. The reason for all this idle speculation of course, is how far can I glide after an engine failure? At 6,000 feet in zero wind, a 9:1 ratio would get you 9 nautical miles to the ground.

Is that 9:1 with a windmilling prop? Who knows, since the glide ratio data for this airplane isn't published anywhere I can find. Stopping the prop would involve slowing down to close to stall and possibly yawing one direction or the other. Stopping the prop should help the glide ratio 15 to 20 percent, as a WAG.

Has anybody out there experimented with this kind of thing? Russ Farris

zero.one.victor · Post by **zero.one.victor** » Mon Nov 29, 2004 6:48 am

The POH for my old 150 stated that the glide ratio was 8:1. I figured that meant for every thousand feet of altitude I could glide about a mile and a half-- given "perfect" conditions, that is.
After having a connecting rod break in flight, out over the salt water no less (

), I have to say that I don't believe it. From 1700 feet MSL, I limped about 2-1/2 miles to an airport at 240 feet MSL, and that was with the engine still making partial power. Or at least some noise.
Glide ratio's are like right-of-way rules-- they're fun to talk about, but they don't necesarily mean anything in the real world. What does count is the real-life "best glide" speed. Theoretically, this should be the same as vy (best rate of climb speed), which I think is supposed to be about 89 mph for the various 170 models. You get what you get as far as the actual descent rate.

Eric

Robert Bishop · Post by **Robert Bishop** » Wed Dec 01, 2004 8:46 pm

I understand that the C 170 can glide all the way to seen of the accident!

N170BP · Post by **N170BP** » Wed Dec 01, 2004 9:20 pm

Not only that, a 170 can glide with nothing forward
of the firewall being there! (no motor mount, no
engine, no cowling).

I know of at least 2 cases where the FWF came off
of a 170 in flight and both glided to the ground.

Dave Clark · Post by **Dave Clark** » Wed Dec 01, 2004 11:57 pm

Bela, I wonder if it could do that with a more aft cg loading? The only way I can see it working is with a fwd cg.

N170BP · Post by **N170BP** » Thu Dec 02, 2004 6:01 am

I agree, there's no way I'd believe it unless I had seen it myself.

I helped recover the 170B / c-210 midair that occured earlier
this year near Tenino, Washington State (the C-210 ran over
the top of the 170 in cruise flight at 3500 feet MSL).

It knocked the front end off of the 170 clean (the engine was
found about 1500 feet away from the rest of the wreckage).
Amazingly, the 170 pilot survived, and described his dead-stick
glide to eventual crash landing with great detail.

There must be enough elevator authority in the 170 sans
FWF to at least effect a "falling leaf" path to the ground.
In the aforementioned case, if the pilot wouldn't have hit
a telephone line strewn across the entry paty to his intended
"crash landing" site, he would have landed without so much
as a scratch to his person. As it was, he hit the telephone wire
and the airplane flipped over on it's back as it crashed to
the ground. I understand he walked away with a bloodied
face, but other than that, none the worse for wear.

The other example I refer to, I don't have any 1st hand knowledge
of, it was just related to me by a close friend who (I believe) has no
reason to fib / make big stories up. In this case, the 170 in question
shucked a prop blade in cruise flight, which promptly tore the
nose of the airplane off. It was able to glide to an airport/runway
and land successfully (if I have my information right, this happened
years ago at Felts Field).

N170BP · Post by **N170BP** » Thu Dec 02, 2004 6:07 am

Forgot to add that while picking through the wreckage for
personal effects, it was noted that (goes without saying) the
pilot was by himself, but the airplane was loaded with a couple
of suit cases + various personal effects.

I would say the aircraft I saw was fairly lightly loaded (under 200lb
pilot, 1/2 or less fuel, maybe 100 to 125 lbs of baggage in the back).

In other words, it might be said that it wasn't particularly loaded with
what you might call an overly forward CG.

zero.one.victor · Post by **zero.one.victor** » Thu Dec 02, 2004 7:00 am

I had heard about the first wreck Bela mentioned at the time from Bela, and (no offense) didn't believe him about the engine coming off in the air. Seems like the airplane couldn't help but go into a tailslide attitude from the CG change. I later corresponded via email with the kid (Gharyn Loveness) who was flying it. He confirmed Bela's story, says he coulda landed OK if it weren't for the wires.
About a year before he'd been in an airplane wreck that beat his face up pretty severely & killed his dad. He's pretty lucky for surviving two unlucky situations.

Eric

russfarris · Post by **russfarris** » Mon Dec 06, 2004 5:29 am

I still think having some idea of what the glide ratio is might make the difference between an emergency landing on an airport instead of some plowed-up field. I did like Eric's comment about right-of-way rules; my mother once said the right-of-way belongs to the most aggressive driver...

Engine failure at 7,500 feet AGL! No wind, best glide speed 80 MPH. Prop windmilling. How far can a 170 glide? Let's see some estimates here, then I'll post mine. Russ Farris

zero.one.victor · Post by **zero.one.victor** » Mon Dec 06, 2004 6:38 am

I'd say 10 to 11 miles, based on my old mile-and-a half- per thousand rule. Of course, with my luck, the only suitable landing site wold be 12 miles away!
An aquaintance of mine was passenger in a Lancair recently that experienced fuel exhaustion a couple months ago,over near Spokane. They had a couple hours of fuel on board whe they took off, but when they put down the gear to land after about 45 minutes of flight, the engine just flat quit. I imagine the pilot/owner was in the habit of flying a big, fast, flat pattern. Never did figure out what happened to all the fuel. Anyway, they landed short of the runway, the airplane was totalled, and the 2 guys onboard were beat up some--luckily nobody was killed or even seriously injured. I don't know what the moral of the story is, except maybe expect the unexpected.

Eric

Dave Clark · Post by **Dave Clark** » Mon Dec 06, 2004 12:19 pm

Of course, with my luck, the only suitable landing site wold be 12 miles away!

What do you mean Eric....you made it to an airport didn't you

zero.one.victor · Post by **zero.one.victor** » Mon Dec 06, 2004 4:56 pm

Yeah, that's true: this time anyway! That doesn't always guarantee things-- the wreck I mentioned earlier in which Gharyn Lovenesss dad Gary was killed: his turbine Bonanza ran out of fuel near the Wenachee area, he managed to glide to a clearing where he attempted to land. I guess he ran out of room, and hit an enbankment, & that was all she wrote. I'm always so happy to hear about not only a successful forced landing, but one where no one is hurt & the airplane is even usable again!
Speaking of which, yesterday's news showed a 185 that crashed at the Renton airport, killing the pilot. Sounds like maybe the engine quit or was failing in some way, and he got too slow & into a stall/spin situation.

Eric

N1478D · Post by **N1478D** » Mon Dec 06, 2004 5:57 pm

FWIW, the old saying that after an engine problem there are more accidents were after the pilot has success in gliding to a runway location he/she overshoots and runs off the departure end vs coming in too short and having an accident at the aproach end probably has merit. It sure is hard to give up altitude when you are all hot because the fan has stopped. Don't ask me how I know, but trust me, the temptation to come in high is sure there. If you survive that, it's one of those things that you will only do once - having the end of the runway coming up fast kind of sticks in your memory. Someone once posted here that the best thing is to set up as normal of a pattern as possible - well, some people's normal pattern is pretty damn big - practicing engine out landings is fun and can really pay off but then again, it's somewhat different in practice than it is when it really happens.

zero.one.victor · Post by **zero.one.victor** » Tue Dec 07, 2004 12:55 am

Overshooting is no good, but undershooting ain't any good either! I know of another fatal wreck around here a couiple years ago where the airplane augered in ( literally! ) short of the actual runway, in an over-run area. I think that he was trying to stretch the glide to make it to the runway, got too slow, and stall-spinned it in.
That dead-stick business has to be just right, unless you're lucky enough to have several thousand feet to work with.
A few years back, an old guy I know had a forced landing in his C-195 on the first flight after several years of (kinda) restoring it. I think he turned the fuel selector the wrong way after take-off, but he's never admitted it. Anyway, he calmly plunked it down into a cow pasture about 3 miles from our airport. Not only kept it in one piece, but, avoiding the peat bogs in the area, landed it where he could actually take off again! Neat trick!

Eric

TP · Post by TP » Wed Dec 08, 2004 12:24 am

When I was a student I had engine out landings pounded in to my head. The reason for this I was told was because people blow that on there check ride all the time. So I got in the habit of making all my landings simulated engine failures. Still do it at untowered fields. Good habit, bad habit I don't know. If I ever lose a engine I'll let you know if it pay's off.