Best Glide, Minimum Sink... how about Minimum Energy?

I'd go for minimum energy landing with my PARACHUTE
 
Erice said:
I know this thread is about how to AVIATE. If there is time, don't forget the NAVIGATE-COMMUNICATE part. If you are in touch with ATC (you were on an IFR flight plan if you were in IMC, right?), and your radio still works, declaring an emergency and asking for vectors to the lowest terrain might be wise, especially if you don't have the terrain-aware GPS. Then, if your impact is survivable, you might have a better chance of being rescued. I might even just hit the Ident button as I am talking, if I felt I was too overloaded to tune to 7700.
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Does ATC know anything about terrain except the MVA? I don't think so, or perhaps better said, I wouldn't count on it.

Absolutely, declare an emergency, and activate your 406 MHz ELT on the way down. Only have a 121.5? Well ATC should have a rough idea where you are, so AFRCC should launch a mission.
 
ALWAYS cover your bet...
Do not fly into 0-0 IMC - knowingly...
Try to always have a bit more than 200 foot of ceiling... Every foot is precious when looking for a flat spot...
Do not mix low ceiling IMC and night conditions - double whammy...
Do practice power off landing to a spot every 90 days...

denny-o
 
Dr. O said:
ALWAYS cover your bet...
Do not fly into 0-0 IMC - knowingly...
Try to always have a bit more than 200 foot of ceiling... Every foot is precious when looking for a flat spot...
Do not mix low ceiling IMC and night conditions - double whammy...
Do practice power off landing to a spot every 90 days...

denny-o
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LOTS of early summer mornings in PA, MD, WV, NY you will be in severe clear at 5,000 with 200' of 0-0 covering the ground in the valleys below.
 
I would trim for best glide with the prop course while leaving the gear and flaps up.

Reasoning:

POH - FORCED LANDING NO POWER
Airspeed 75 Flaps 0
65 Flaps 30
Full Flaps recommended
Gear Down (Up if Rough terrain or soft field)

Best glide puts me right in the normal and recommended landing speed range.

1850 lbs (Empty plane and me) 61 knots
2650 lbs (Full plane at max weight) 73 knots

At this speed the RG without any drag does not want to come down.

I remeber reading an article that the full up trim was a quick way to get the airplane configured at close to best glide without giving it much thought.

I wonder about putting the landing and taxi lights on in the clouds in order to try and see when and once you break out. Any thoughts on that?
 
Definitely a difference for flying over the mid-west where it's very flat vs. flying over mountains.

Having something with terrain data could help here. If you've got a GPS that will show you some flat areas (or some straight highways) then those might give you your best chance of a survivable landing. Over a city or other populated area? I'd want to glide away from it.

All that's a lot going on when your engine quits, though, and I'm with Jesse - I think more likely most of us would end up being focused on flying the plane. Getting these airspeeds perfect is a nice idea, but probably not terribly realistic.
 
Ted DuPuis said:
Definitely a difference for flying over the mid-west where it's very flat vs. flying over mountains.

Having something with terrain data could help here. If you've got a GPS that will show you some flat areas (or some straight highways) then those might give you your best chance of a survivable landing. Over a city or other populated area? I'd want to glide away from it.

All that's a lot going on when your engine quits, though, and I'm with Jesse - I think more likely most of us would end up being focused on flying the plane. Getting these airspeeds perfect is a nice idea, but probably not terribly realistic.
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Since "Best Glide" varies with weight, it will be tough to even know the exact airspeed, let alone fly it perfectly.

I don't think anyone's advocating that. I think it's more a mental exercise from the comfort of the keyboard. :D

But you can be close enough. As others have mentioned, going with full nose up trim (if that works in your airplane) is probably close enough for this sort of situation.

If that gets you too slow, then adjust after you've gone through the restart procedure.

If that fails, fly as close to stall as you can when you think you're near the ground to reduce F=M*A and hope for the best!
 
In a number of aircraft getting the speed too slow will result in an excessive sink rate. Mooneys come to mind for that. The danger of getting close to stall speed is less the stall (which I've found to be very docile), it's the high sink rate you'll get and not necessarily notice. I did have that happen to me once on the M20F I flew early on, where I realized I had a high sink rate on final close to the ground. Added a bunch of power to cushion it out. Rough landing, but nothing bent.

I haven't played with it in the Aztec too much, but I don't let the thing get too slow since I want to stay well above Vmc, and generally stay above Vyse. My minimum sink rate on that thing with both engines out is roughly equivalent to a brick, so best to keep at least one running. I know the scenario is all engines fail for whatever reason. While that does happen, it's not a particularly likely scenario.
 
dmccormack said:
Since "Best Glide" varies with weight, it will be tough to even know the exact airspeed, let alone fly it perfectly.
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Varies with wind as well (assuming that by "best glide" one means the speed at which one will cover the maximum distance over the ground).
 
Capt. Geoffrey Thorpe said:
Varies with wind as well (assuming that by "best glide" one means the speed at which one will cover the maximum distance over the ground).
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True! And that's another data point that will be inexact and will have to be guesstimated.

In the Army we had a saying, "Close enough for hand grenades" -- roughly translated, when you're close enough to be launching hand grenades, you don't worry about poinpoint accuracy.
 
dmccormack said:
I don't think anyone's advocating that. I think it's more a mental exercise from the comfort of the keyboard. :D

...
If that fails, fly as close to stall as you can when you think you're near the ground to reduce F=M*A and hope for the best!
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Exactly. The question I was embedding here was the difference between airspeeds such as best glide or minimum sink, and what they translated to in terms of impact energy.

Tony nailed it with his diagram - Minimum Controllable Airspeed (at least for his airplane) appears to yield minimal energy. So that's what you want at impact. Everything else is a tradeoff between stall margin and impact energy. But we did see that best glide is NOT a minimal energy airspeed.
 
It is good to learn from Tony's diagram that you can't trade sink rate for for forward speed or reverse. I thought for a moment that by knowing (or estimating) the type of terrain you will be hitting you could perhaps pick a smaller sink rate but higher speed (clear fields) or high sink rate but smaller forward speed (trees). It turns out that for all practical purposes you get both at the same time - minimal sink rate with minimal forward speed. It is always good to know, just in case.
 
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One thing about the full aft trim thing is that we do in "training mode" with only one or two people onboard and in the front seat, and so with a forward CG.

Take the bird out with a bunch of stuff in the baggage compartment and get the CG aft, then try it and see what happens. You can get into VERY slow speeds and develop a very high sink rate.
With some aircraft with *very* wide CG envelopes, the same trim setting will give you very divergent speeds depending on where the CG is.
Imagine a Cherokee Six with only two people onboard and in front, vs two people in the rear sets and a weekend of luggage in the rear baggage area. Or a Skyhawk with a person in the back and luggage in the rear.

More people get in trouble because they try things in "training mode", then need to apply them in "family truckster" mode.
 
PilotAlan said:
One thing about the full aft trim thing is that we do in "training mode" with only one or two people onboard and in the front seat, and so with a forward CG.

Take the bird out with a bunch of stuff in the baggage compartment and get the CG aft, then try it and see what happens. You can get into VERY slow speeds and develop a very high sink rate.
With some aircraft with *very* wide CG envelopes, the same trim setting will give you very divergent speeds depending on where the CG is.
Imagine a Cherokee Six with only two people onboard and in front, vs two people in the rear sets and a weekend of luggage in the rear baggage area. Or a Skyhawk with a person in the back and luggage in the rear.

More people get in trouble because they try things in "training mode", then need to apply them in "family truckster" mode.
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That's an excellent point, though -- as mentioned earlier -- if the trim is set to full nose up, the speed should be monitored and the trim reduced somewhat to maintain the desired airspeed.
 
dmccormack said:
That's an excellent point, though -- as mentioned earlier -- if the trim is set to full nose up, the speed should be monitored and the trim reduced somewhat to maintain the desired airspeed.
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No disagreement.
My point wasn't so much about the trim thing, it's about the fact that when we go out and practice things (stalls, short field landings, whatever) the behavior of the plane in training mode is very different from traveling mode.

How many people go out and load junk in the plane to get it to gross, then go practice their short-field technique? How many practice approach and departure stalls with an heavy plane with an aft CG? I know I did after I finally was able to buy my own plane.

I really think this contributes to the departure stall and other accidents accidents that leave us all scratching our heads. It's almost like practicing winter driving techniques on dry pavement, then being surprised in the first blizzard when the car doesn't turn when you turn the wheel.
 
PilotAlan said:
No disagreement.
My point wasn't so much about the trim thing, it's about the fact that when we go out and practice things (stalls, short field landings, whatever) the behavior of the plane in training mode is very different from traveling mode.

How many people go out and load junk in the plane to get it to gross, then go practice their short-field technique? How many practice approach and departure stalls with an heavy plane with an aft CG? I know I did after I finally was able to buy my own plane.

I really think this contributes to the departure stall and other accidents accidents that leave us all scratching our heads. It's almost like practicing winter driving techniques on dry pavement, then being surprised in the first blizzard when the car doesn't turn when you turn the wheel.
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Agreed!
 
Hmmm, sounds like something new and interesting to do...now where to find 300# of sandbags!

;)
 
TMetzinger said:
Does ATC know anything about terrain except the MVA? I don't think so, or perhaps better said, I wouldn't count on it.
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Actually, they do know quite a lot about terrain. See 7110.65 10-2-17. EMERGENCY OBSTRUCTION VIDEO MAP (EOVM) and 3-9-4:

"An EOVM shall be established at all terminal radar facilities that have radar coverage in designated mountainous areas".

Also some more details about what the EOVM does. 7110.65 is excellent reading, as always!

As for the question: Trim all the way back. That's always minimum sink, and if you don't know that there's a runway-like surface below, that's definitely the way I'd chose.

-Felix
 
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