A different view of flight safety.

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BBerson

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Isn’t minimum sink speed significantly slower than best glide speed?

I think he was saying fly at 1.4 X stall speed which for my plane is about 5 knots faster than best glide speed. No idea what minimum sink speed for my plane is (maybe 5 knots below best glide speed)?

I agree it is better to stay above best glide speed and his 1.4 X stall speed seems about right for me. Heck, that probably approximates best glide speed with a 5 knot headwind.
Yes, minimum sink speed is less than best glide speed, but it's still a safe and useful flight speed. Don't always need best glide to make a dead stick emergency landing. The current airplanes have a mark at stall and stall is always a useless speed to fly. The lower safe airspeed mark should rather be somewhere higher than stall, but where exactly is undetermined.
 

davidb

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Yes, minimum sink speed is less than best glide speed, but it's still a safe and useful flight speed. Don't always need best glide to make a dead stick emergency landing. The current airplanes have a mark at stall and stall is always a useless speed to fly. The lower safe airspeed mark should rather be somewhere higher than stall, but where exactly is undetermined.
I don’t see minimum sink speed as a good option unless you have no safe landing sites and want to maximize time for a restart. Flying a dead stick approach at min sink speed will result in a hard landing at best. I don’t want to get that close to stall speed until I’m close to the ground. You need more than a few knots above stall to effect a round out and flare with no power.
 

BBerson

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I don’t see minimum sink speed as a good option unless you have no safe landing sites and want to maximize time for a restart. Flying a dead stick approach at min sink speed will result in a hard landing at best. I don’t want to get that close to stall speed until I’m close to the ground. You need more than a few knots above stall to effect a round out and flare with no power.
The instant the engine quits the brain needs time to react and find the best option. Don't need a great glide angle. Really, the pilot should be looking directly forward and right and left some for the landing spot. You can never extend the glide if needed if you are already at best glide speed. Don't need best glide speed anyway when landing on a spot below you. Glider pilots set up for landing at a very steep glide angle (maybe 7-1 at half dive brakes). My Grob has a L/D of 30-1. That 30-1 is useless in landing. When I pick a spot to land it is always in view and I pull the spoilers out to set up my 7-1 glide approach to the spot. I can make adjustments as needed to say 4-1 if high or 10-1 if low. (I can go to 30-1 if needed, but that's rare and a sign of a lax glider pilot). So really, my glider approach is using a range of glide angles similar to what an airplane has available.

The point is, a glider comes in high and close and uses all its spoilers or dive brakes to reduce the glide angle.
A dead stick airplane pilot can do the same depending on the situation and altitude using various speeds and slips.
You can pull the stick to increase the glide angle to minimum sink or back to best glide speed to extend. Depending on headwind, might want more airspeed like glider pilots do.
I think his point was the airspeed should have a minimum usable mark. Any speed above that minimum is enough.

For actual best flare speed, that depends on your aircraft drag and your choice. Touching down at best L/D speed is too much energy and speed, normally, in a confined area. So yes, some spare energy is needed to flare. The speeds will change as needed.
 
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radfordc

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The point is, a glider comes in high and close and uses all its spoilers or dive brakes to reduce the glide angle.
A dead stick airplane pilot can do the same depending on the situation and altitude using various speeds and slips.
Yes! I was doing a first flight on a friend's plane and the engine did quit on base leg. I had kept the pattern altitude high on purpose so had plenty of altitude and speed to play with. I kept my speed well above stall until on short final when I went to full flaps and a hard slip. I still touched down fast, but figured better to run off the other end of the runway slow than to end up short of the runway at flying speed. I still got stopped with runway to spare. There is a video of that landing.

 

Turd Ferguson

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When you factor in the two Boeing and the Airbus crashes due to inability to recognize, and recover from, a stall, there may be just as many dead people, over that past two decades, from the airlines’ approach to training as from GA’a approach.
The FAA changed (or rather Paul Kolish convinced the FAA to change) how US airlines recover from stalls after Colgan 3407 crashed in Buffalo. That has now tricked down and is published in the ACS for private pilot evaluation but I suppose it will take a while for everyone to get on the same page. Instead of the old long standing "min altitude loss" criteria, a stall recovery now focuses on reducing angle of attack without regard to altitude loss.
 

Turd Ferguson

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The instant the engine quits the brain needs time to react and find the best option.
Unfortunately that requires periodic review and rehearsal. I always ask pilots during a flight review when was the last time they practiced stall recovery and after a deer in the headlights look, it's disclosed that no stalls have been done since the last flight review. Hard to stay on top of your game when you don't practice.
 

Turd Ferguson

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Thanks, the video was worth watching, and makes a lot of good points. I don't believe, however, that this "minimum maneuvering airspeed" idea will be a valuable approach to reducing GA stall/spin accidents.
GA pilots are already too focused on airspeed as a means of preventing stalls. What are the chances they'll commit more minimum airspeeds to memory and actually use them in a pop-up emergency?
In a lightplane, only one min maneuvering speed value is required. Like the video, it can be pasted on the indicator so there is nothing to remember. At work we have several min maneuvering speeds but we can easily calculate those from the speed cards. (current ref value +10)

I don't think pilots are too focused on airspeed. Not by a long shot.
 

BBerson

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Yeah, thermalling in a glider helps, because the glider is frequently getting into little stalls and the only recovery is a bit of stick forward. I liked to practice dead stick landings with my Chief with the engine at idle.
Departure stall doesn't get much practice. So must be alert on takeoff and ready to do that instant push forward. I tried a practice departure engine failure once in my Cherokee. It just felt like it instantly fell, so I got the power back in immediately before I got to the trees. I won't do that again. Need to practice up higher.
 

bmcj

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Yes! I was doing a first flight on a friend's plane and the engine did quit on base leg. I had kept the pattern altitude high on purpose so had plenty of altitude and speed to play with. I kept my speed well above stall until on short final when I went to full flaps and a hard slip. I still touched down fast, but figured better to run off the other end of the runway slow than to end up short of the runway at flying speed. I still got stopped with runway to spare. There is a video of that landing.
I use the same approach, but IF needed, I will hold the slip all the way to the ground, only releasing it as I flare for touchdown. Here where I fly now, we have trees to clear if the wind blows from the east, so I will come in just over the trees, then kick in a full slip to make the final drop down to the runway.
 

bmcj

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stall recovery now focuses on reducing angle of attack without regard to altitude loss.
Actually, anytime you are climbing slower than your best glide speed, pushing over to zero-g to attain best glide will eliminate induced drag, leaving you with absolute minimum drag during your pushover. Because of that, a hard pushover stands to possibly gain you more glide range simply because you flew to your best glide speed without induced drag sucking up some of your energy during the transition.
 
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BJC

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I don’t see minimum sink speed as a good option unless you have no safe landing sites and want to maximize time for a restart. Flying a dead stick approach at min sink speed will result in a hard landing at best. I don’t want to get that close to stall speed until I’m close to the ground. You need more than a few knots above stall to effect a round out and flare with no power.
I practice the “impossible turn” routinely. The first time I did it at actual altitude to a landing in my then-new plane, as per my habit from my A152, I exited the U turn at best glide speed. That was a mistake, because even with full flaps and a full rudder slip, I used the entire runway. I now fly the turn at less than best glide speed. (Best glide is around 85 knots, minimum sink is around 75 knots, and full flaps stall is around 42 knots.)

The point is that there are many different scenarios, and a single, simplified (“immediately push over ...”), course of action is not always the best action.


BJC
 

Dana

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I thought I posted this yesterday, but it showed up today in the editing window, so I guess not. So it's a bit out of sequence, but anyway:

For a typical powered plane, min sink will be equal or close to Vx (best climb angle), and best (flattest) glide will be equal or close to Vy (best rate of climb). Seems backwards but that's the way it works out.

I'm dubious about the "min maneuvering speed" proposed in the video. He starts with the commonly recommended 1.3Vso, which is already a arbitrary buffer above stall, and adds the increase in stall from an arbitrary 30° bank. Why is any one arbitrary number more valid than any other?

I wonder how many of the pilots who die in stall/spin accidents had gone out and done a few full stalls iin varying configurations on a regular basis.
 

Rockiedog2

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All that's good.
For my use, I've greatly simplified things on my 701. It's always 50 and clean, then 45 with half flaps. That covers Best Glide and Min Maneuvering. I don't care about min sink.

Up high say 500 feet and up, if it's in a 45 degree cone under the plane we can make it no wind. Split the windshield with the horizon and we'll be close to on speed. A quick cross check and adjustment as we're turning toward the spot. That's about it. Head outside almost always, judging the spot, fly the attitude and the speed will be ok. Check the switches, pump on and switch tanks depending. Assuming the prop is turning that's probably all I'm gonna do unless way up there. Fly the thing.

On takeoff leg/early climbout say below 200-300 feet (45 IAS and clean) there's even less to do. Yeah the immediate instinctive pushover bearing in mind it may be sluggish response cause the fan just quit blowing on the elevator, quick check the boost pump/fuel valve while pushing. And on the 701 climbout may be so steep that the pushover maneuver may not go too well so we're gonna be aggressive. One of those things we accept going in for close in obstacle clearance. So shove it over and try to hit whatever is softest and cheapest as slow as possible.Until it's reliably instinctive under stress, always mentally review it before pushing the throttle up. No surprises, we always assume it's gonna quit don't we?
 
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bmcj

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One of the things I noticed in the video was that he set his minimum maneuvering speed based on stall at a 30 degree bank. But what happens if you exceed the 30 degree bank Bank or, worse yet, Skid it around the turn to final? You can still stall plane at that minimum Maneuvering speed.
 

Rockiedog2

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One of the things I noticed in the video was that he set his minimum maneuvering speed based on stall at a 30 degree bank. But what happens if you exceed the 30 degree bank Bank or, worse yet, Skid it around the turn to final? You can still stall plane at that minimum Maneuvering speed.
Well, shoot! Try as we might to get around it nowadays,we still gotta fly the thing don't we? :(

Does the current crop of instructors still train to assume engine failure on every takeoff? From what I've read here, that thought might be enough to make both the IP and student quit.
At my airport there's only one decent place for a forced landing and that's the 250acre field next door. So every departure is routed to set up for that field. That also happens to be the best noise abatement route for my neighbors so that's what we fly every time.
At out home/frequent airfields we should know where we're going if it quits for every runway. Do they teach that nowdays? The big boys brief that for every takeoff and they got less likelihood of a failure that we do in our pistons.
 
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BBerson

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One of the things I noticed in the video was that he set his minimum maneuvering speed based on stall at a 30 degree bank. But what happens if you exceed the 30 degree bank Bank or, worse yet, Skid it around the turn to final? You can still stall plane at that minimum Maneuvering speed.
He said the Defined Minimum Maneuvering Speed would be 1.4. The stall at 30° bank is 1.08, I think.
 

Pops

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I was taught that every takeoff is a, WHAT IF, takeoff. Already have a plan of action is it gets quiet. And I have had a engine failure on takeoff.
Taking off of KCRW on runway 23, when going off the end of the runway you are instantly about 400' above the city and only place to go is in the river or a heavily traveled interstate. I'll take the river.
Some people has flown past the airport, over the river and several hundred feet below runway elevation and radar and tower could never see them.
 
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12notes

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One of the things I noticed in the video was that he set his minimum maneuvering speed based on stall at a 30 degree bank. But what happens if you exceed the 30 degree bank Bank or, worse yet, Skid it around the turn to final? You can still stall plane at that minimum Maneuvering speed.
Actually, he sets minimum maneuvering speed by adding the load of a 30 degree bank on top of 1.3 Vso, not stall in a 30 degree bank. He ends up with 1.404 Vso, which is approximately stall speed in a 60 degree bank. This will allow for some pretty stupid maneuvering without killing the pilot.
 
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