Engine Out Glide Distance?

[N297NW]

Last week end, I flew 250 miles home in my RV-8 on one of the most beautiful VFR nights I have ever seen. Not a cloud in the sky and stars everywhere. I was flying at 8,500 feet and could see city lights that were miles away. Truely awesome.

I started fiddling with my GNS-430 and found the nearest airport information. I noticed that at that particular point in time, the nearest airport was KMRB at about 11 miles. It occurred to me that I didn't have the slightest idea how far I could glide if the motor stopped. Is it five miles? Ten? I guess I just need to go and try it.

So my question is this. Does anyone have a rough planning figure for this situation:

7,500 feet AGL
no wind
reasonably good pilot who pitches to best glide and keeps it there

I am not looking for a formula or an exact figure, but rather some real-world experience so that the next time I look at that GPS info I can quickly judge whether in an engine out scenario to head for that airport or look for another option.

Thanks,

bruce

[aparchment]

I am looking forward to a more accurate answer than I am about to give, but I use 10:1 in the planes that I currently fly since this makes cockpit calculations simple for me.

So at 8500' of altitude AGL you have 85,000' of horizontal distance. If we round a mile to 5,000' then you have 17 miles. I figure round down to compensate for the rounding error, adrenaline and mistakes, so figure 15 miles in a no wind situation.

Of course it's key to know your altitude AGL as opposed to MSL.

Hope someone can recommend a better way that's simple to use in an emergency.

Antony

[aparchment]

One of the planes I fly has dual Garmin 430s. On cross countries over less populated areas, or at night I use one 430 for nav functions and one is set in nearest airport mode. Paranoid perhaps, but I like the situational awareness. I also run the rough calculation above at regular intervals just to keep my mind active. It's pretty easy to get lulled into complacency on a long flight, and speaking from personal experience, the adrenaline really spikes when you go from complacency to dealing with a potential emergency.

[Kahuna]

Originally Posted by N297NW

So my question is this. Does anyone have a rough planning figure for this situation:

I am not looking for a formula or an exact figure, but rather some real-world experience so that the next time I look at that GPS info I can quickly judge whether in an engine out scenario to head for that airport or look for another option.

bruce

Bruce,

Get over an airport and pull the mixture. It is no big deal. Pull the mixture and the motor quites producing power, push it in and it fires right back up. You should know the glide ratio for your plane and the fact that you ask about it means you are in fact concerned as you should be. JUST DO IT MAN! You will be glad you did. Dont fear the red knob. Practice gliding with the engine off. Dont wait until you have no choice. It is actually quite fun after you do it a few times. You will find you have both a fun RV and a fun glider.

8.3:1 in my S8 at near gross 1900lbs

Kahuna

[n468ac]

in our tests we found 1000' per min, was about best glide.

I my judgement ... it's not really how far you have to go to the airport ... it's how long you have to decide where to land.

I like to fly around 8500 and in the chicago area we are around 600 MSL.

so at best i figure i have 8 mins to fix the problem or land ... in tests 8 mins isn't very long.

[ship]

imho 10:1 is probably a bit optimistic for "power off" glide in the short-wing RV's (all except RV9)... one major factor is f/p vs. c/s prop....a c/s prop will windmill at flat pitch causing more drag than a f/p prop thus faster sink rate

mike stewart's numbers are enlightening.....if you're idling you'll probably see 10:1 but with engine truly leaned out the sink rate will increase dramatically especially with c/s prop i.e. stewart's #'s in the low 8's

try actual engine-out at different weights and see what happens....my guess is that each 100lbs reduction will gain appx .25 ft/ (short wings = small gain in glide for each pound lighter)

i use 10:1 in Cherokee 180 (heavier but higher aspect-ratio wing than RVs)

i plan to use 8:1 (RV8 180 c/s) to ensure a solid margin

RV9 should glide better given the longer wings & lower wing loading

one last thing: making any turns in a glide will increase the sink rate ...make sure to add some "turn" margin into any glide planning assumptions since you will rarely be lined up with a runway when the engine quits (and the engine will always quit with a headwind )

[szicree]

I'm sure most know this, but for those who might not, speed for minimum sink is not the same as speed for best glide. I guess which you use depends on the situation, but 11 miles out at 8500 sounds pretty far to me.

Steve Zicree
Fixed pitch Day VFR RV4 with wires all over my garage

[Bob Axsom]

My 6A has a 24.5' wing with the extra tanks but it is heavy and it has a C/S prop. When I pull back on the throttle it feels about like the Space Shuttle. In case of power failure (yes I have) switch tanks, turn the aux. fuel pump on, try to get it restarted and do the best job I can to assure my survival of the power off landing if it doesn't. My plane glides but if I wasn't high and close to an airport I would eliminate that option quickly. 1,000ft/min sink rate is extremely optimistic in my plane and the probability of an engine failure coincident with the presence of an airport within glide range is low. It is the first item ticked off in my survival reaction thinking. If you are keeping track of your progress cross country with a moving map display you know where the surrounding airports are and you can see which one is the closest so whether that is an option or not should be dealt with pretty quickly. It has to be a comfortable angle, 45 degrees or better, down from the airplane to the airport before I would expect to make it. The original question is a good one "what is the best glide speed" - well In my plane I would go for 85kts until I was getting close to an off airport landing then I would have it closer to 60kts to try to enjoy the flight a little longer and soften the blow. A friend of mine was killed when the checkout pilot made and emergency landing off airport on upsloping terrain near Irvine California with the gear up. The resulting pancake impact on his body was more than it could stand so getting slow is not always the answer. The fixed gear on an RV should allow you to survive a pancake landing off airport so I would go for "slow but no stall" near the end.

Bob Axsom

[L.Adamson]

Originally Posted by Bob Axsom

The fixed gear on an RV should allow you to survive a pancake landing off airport so I would go for "slow but no stall" near the end.
Bob Axsom

Last winter, just a few miles from my home, a Cessna 310 fighting some head winds on a long cross-country, decided to make an un-scheduled fuel stop. He was following a mountain ridge line east of KSLC, with clouds and haze below. Decending to the airport, he flew into what looked like a broken cloud with terrain below, but the terrain was actually a lower elevation mountain perpendicular to the ridge he was following. Realizing he was headed directly into a 45 degree upslope, he poured in full throttle to both engines, and hauled back on the yoke. Within nearly the same second, the stall horn blared as the plane hit the upslope at nearly the same nose high angle.

Of course, in this case, hauling back on the yoke..........is the only option, since terrain is just a few feet away! And this time, it was exactly what worked. The aircraft hit the mountain at a near 45 degree angle and rather slow airspeed, then sunk in a wingtip & cartwheeled over.
It settled just a few hundred feet above a subdivision.

Luckily, there was just a few scrapes to both the pilot and his passenger. This is just an incident, where the plan wasn't to stall the aircraft, but being right next to the rising terrain, and the effect on slowing the foward motion by stalling----- worked.

And BTW- about 12years ago, we had a student pilot stall a Cessna 152 into a tree in the middle of a crowded shopping center parking lot. The tree was the only option, and pulling back at the moment of immenent collusion worked there too. The student, also, just suffered a few scrapes & bruises, and the plane stayed mostly intact. This accident was a result of not adding enough fuel for a return cross-country.

I guess somebody needs to research these cases, and write a book, about the few times where a last second stall can be a life saver.

L.Adamson

[gmcjetpilot]

It is academic to a point but my advice is practice an occasional power off approach and landing.

By all means have a glide ratio in mind, something simple you can use, like for every 1000 feet altitude you can glide 1-1/4 kt mile, or even 1000 foot to 1 kt mile, something conservative to account for wind and maneuvering.

All the facts and figures in the head will not do any good if you don't practice. G