Forced Approach - Best Glide Speed

[Cat Driver]

One of the most interesting factoids I noticed about how most flight instructors think when I had them in my employ was their fear of what Transport thinks.

T.C. is like a religion, they motivate the sheep through fear.

When faced with a forced landing due to engine failure the last thing anyone with any ability for critical thinking will worry about is what Transport thinks

[Adam Oke]

Best Glide is the tip of the ice burg. Most glider pilots hardly ever use best glide and are more concerned about effects of wind and how it effects the glide ratio. If you read up about polar curves, this will give you some insight. It's all about penetration .... not a specific speed.

If you're at your best glide, and not going anywhere because of the wind ..... lower the nose and punch through the wind. This will effectively increase your glide ratio. Lower the nose as much or as little as you need to make the field (within reason). Just be sure to use all of your bag of tricks to make the field.

[Pop n Fresh]

Git to work on that RV so you can bring it out here to lurn me some glidin.

I'll feed you steaks and some crescent rolls.

[PilotDAR]

"best" glide speed. "Best" for what? Perhaps the pilot would like to make it to shore, thus "best" would be greatest distance achieved for vertical descent. But this speed will hardly be "best" for a safe flare and landing. A faster speed will be better for that.

I discussed this theme in my thread on "height velocity curves" for light planes. There are speeds at which one could glide, which will certainly not result in a safe landing in some conditions.

[Pop n Fresh]

Amazing! Your wife will watch Monty Python with you?

Went quite well. It was kind of like live theatre broadcast so she liked that. There was a older lady beside her doing commentary and laughing so she liked that. She loves popcorn and going to movies so she liked that. The digital feed did not record properly so they gave everyone passes and being more than half Scottish she loved that.

She then went on to claim, "I've watched Monty Python movies. I knew some of those songs."

It was pretty good. If they are still re screening near you I recommend going. I'm not certain it's DVD worthy unless you are a collector.

[iflyforpie]

I read somewhere that Sulley set the plane up for Best Endurance (just below Best Glide) to give himself time to think and the cabin crew time to prepare when he realized he wasn't going to make an airport.

Best Endurance is also good with a tail wind, since you will cover more distance than Best Glide.

Into wind, you want Best Penetration, which IIRC is about 1/4 of the headwind added to Best Glide.

But yeah, no point in messing around if you've got a field in range.... just don't screw it up.

I didn't use best glide for my real forced approach. I cranked it until the stall horn went off to turn back to the field and pitched for a normal power off approach speed. I made the field, and didn't put a scratch on the aircraft.

[Colonel Sanders]

I didn't use best glide for my real forced approach. I cranked it until the stall horn went off to turn back to the field and pitched for a normal power off approach speed. I made the field

Sharp flying, IFP! Congratulations on
really learning to fly, despite what you
were taught.

[AirFrame]

I didn't use best glide for my real forced approach. I cranked it until the stall horn went off to turn back to the field and pitched for a normal power off approach speed. I made the field, and didn't put a scratch on the aircraft.

You turned back to the airport after an engine failure? But... but... that will kill you!

[Colonel Sanders]

Anytime you're going 100 mph or are
100 feet off the ground, you have enough
kinetic or potential energy to kill you.

It's odd how people think some maneuvers
are more Politically Correct than others.

A doctor near me, tried to fly an vectored
ILS one night. He and his pax are dead
now. But people are still flying ILS's, last
time I checked.

But if you teach someone the EFATO, you're
a Bad Person. Much screeching and honking
ensues.

How odd.

I use 90 degrees of bank in the circuit, all
the time. Never stall. Never even implode
with a singularity caused by infinite G. Hell,
I fly the downwind inverted.

This makes you a Bad Person, if you
develop skill and knowledge.

I have never understood the peculiar calculus
of Political Correctness, which seems in no
small part to be advocating ignorance.

www.pittspecials.com/articles/bank.htm

[Big Pistons Forever]

You turned back to the airport after an engine failure? But... but... that will kill you!

Yes unfortunately that is the all to common outcome, like the tragedy at Nanaimo last weekend.........

[CpnCrunch]

ifly: what height were you at when you turned back?

[Rudder Bug]

ifly: what height were you at when you turned back?

That's a good question, I'd like to know as well...

RB

[cgzro]

Most of the planes I fly have poor visibility forward and best glide does not improve visibility. I would want to be banking and slipping to look and find the best field possible rather than glide as far as possible to a bad field. In fact many years ago I had this lesson brought home when an evil instructor pulled the power right over a beautiful private grass strip that i could not see.

[Shiny Side Up]

PUT ON THE SHOULDER HARNESS

I actually had a debate (via email) with a noted expert regarding this, since it was their opinion and experience that you might want to not have it on so you could bail out quicker upon coming to a stop. I know a guy who was killed in what should have been a survivable crash not wearing one, so needless to say I had a differing opinon.

Either way, there might be a lot of ways and things you might do on a forced approach that depend on your circumstances when it happens. I had one once where just holding the glide was just right to get it to the runway. In that case, it might be argued that getting that under control to stretch the last bit of distance out of it was the solution. Might not always be.

The chief problem is that the forced approach, like a lot of things has taken on a life of its own for the purposes of the flight test, and has gotten farther away from the reality. Lets be honest, the excersise isn't representative of most forced approaches, and really only what it might be like in a reasonably glideable piston four-seater. Needless to say you won't be able to cover all scenarios during the training for a PPL, and as you're fond of pointing out its more important to train them how to avoid having to end up in a forced approach.

When I teach instructor students, basically every flight ends up in a forced approach to the runway. That ends up with a lot of scenarios and a lot of things to think about. Its also not the canned precision 180 exersise. They do it with crosswinds, tailwinds, from any position I know we can glide back. We'll do turnbacks. The thing is though, like anything, to be proficient at this sort of skill, you do it over and over and over, ad nauseum. Most PPLs, though, the last time they might do this practice is going to be on their flight test anyways. Do you think in the average PPL's less than 30 hours a year they're going to spend much time keeping this sharp? Not likely. The only thing that teaching "get it gliding" does, is hammer home the get the freaking nose down, and hope that if it happens in the rest of their years flying that they'll remember that.

Something interesting on the topic: Cessna neatly provides for one a cloud breaking procedure, which incidentally works good as a forced approach procedure if one was unfortunate enough to have one at night or in cloud. It sets the airplane up so it descends at a low rate in a slightly nose up attitude. The idea being that if you're likely to run into something on the way down, it puts you in a favorable way to crash the airplane. Lowest forward speed. Keeps the pilot from putting it into a spin by telling him to keep his damn hands off the controls. Reminds him to do up his seat belt. In some ways, its what should be taught to most PPLs who aren't going to maintain proficiency so realistically they can more survivably crash airplanes. Not that crashing airplanes is cool, but then I don't view maintaining a minimum proficiency at what is a somewhat risky activity cool either. Your opinion may differ.

[Colonel Sanders]

See "Tale of Two Comanches".

Despite all the obfuscation, avoidance of
unintentional stall/spin is the most important
objective of any forced approach.

It's really very simple:

If you accidentally stall/spin during a forced
approach, you will almost certainly die.

If you do not stall/spin during a forced approach,
you will almost certainly live.

I find it greatly disappointing that after all
these decades of poor performance on flight
tests and in real life, so little emphasis is
placed upon this. So little is learned. Mistakes
are repeated, year after year, decade after
decade.

Instead, we have people doing all sorts of
useless, distracting housekeeping in the cockpit,
instead of:

FLY THE AIRPLANE

and

PUT ON THE SHOULDER HARNESS

Learn to ruthlessly prioritize. No f__ks given
to people who are trying their best to distract
you from doing your job.

This guy lost an engine after takeoff. How well
did he prioritize?

http://www.youtube.com/watch?v=YqmomTUVsAw

[Docbrad]

I never like watching when you post these types of videos, but I always do. There's a lesson to be learned... Gotta fly the airplane. That's #1

[iflyforpie]

I was at about 300'.

I was fortunate to have a light headwind, and even more fortunate to have a powerful aircraft well under max gross that was able to make that height a decent distance from the field. Fully loaded on a hot day in an anemic aircraft, no way you are making it back.... fancy skills cannot change the laws of physics.

Also..... fortunately..... I was taught that maneuver by a Class 1 Aerobatics instructor during an Emergency Maneuvers training course I was provided with by a previous employer.....

Like CS says..... so many pilots try to teach themselves surface level aerobatics in the few seconds they have before hitting the ground.

[Colonel Sanders]

I was taught that maneuver by a Class 1 Aerobatics instructor

You are lucky to have received some competent
flight instruction. It is getting rarer and rarer,
these days. I thought you had figured it out on
your own, which impressed the hell out of me

I learned to do the turnback from a Professor
(now retired) at the USN Academy, a guy called
Dave Rogers, who did some interesting research
into this particular maneuver. God, that must
be 25 years ago now. And still, no one understands
it. How depressing.

Teaching EFATO turnback is very politically
incorrect. You must do it quietly, for some
bizarre reason. Eric and I have thought of
making a Youtube video, with ground briefing
and footage from inside and outside the aircraft,
but it's just not worth the hassle we would
get for it.

Like a +ve G aileron roll, the turnback is a
childishly simple maneuver. I can generally
teach anyone to do either one, in under five
minutes. But still, people come to terrible
grief with them.

At the risk of annoying more people, could
I say three words, which the Queenair pilot
could have perhaps thought about?

LOWER THE NOSE

After an EFATO in either a single or twin, you
must

LOWER THE NOSE

to maintain flying speed. More correctly, to
keep your alpha down. Don't overdo it and
go -ve G, for chrissakes. Just let it float down.

Very light G, if you are interested.

Learn to do that maneuver wings level. Then
learn to do it while you are also turning, at the
same time.

If you are gentle with the aircraft, fly it with
light G, your stall speed is very low.

In fact, I can fly any aircraft (at low altitude,
the wings have no eyeballs) at 80 degrees of
bank without stalling it ... as long as the G is
low.

Specifically, the stall speed of any aircraft in
a 80 degree banked turn, at zero G, is ZERO MPH.

It is a tragedy that 99% of pilots do not understand
this little detail. They spend their entire lives,
using airspeed as a proxy for AOA, which saddens
me.

Once you start thinking about the wing, and using
the Cl curve, you can do magical things with an
aircraft, which will frighten your friends and get
TC on your case, for the rest of your life.

http://www.youtube.com/watch?v=Fcy4ZhGHHaE

It can get depressing, sometimes. Over 50 years
ago, my father was teaching the same lessons about
the difference between airspeed and AOA, when he
was an instructor pilot on the F-104, to transitioning
Sabre pilots. They had heard that the -104 was a
fire-breathing dragon that could not be slowed
down safely.

Male Bovine Excrement, my father would say, and
they would pitch vertical, throttle back and when
the ASI dropped below 40 knots, do the prettiest
"stall turn" (he calls it - hammerhead) in the -104,
watching the equivalent AOA indicator the entire time.

In the vertical downline, leave the throttle idle, go
supersonic and pull level again.

Anyways. I guess we are Bad People in my family,
but we can sure fly a f__king airplane.

Ninety-seven years in aviation. Maybe - just maybe -
we might have a clue.

[rob-air]

CS the ideas you put down on virtual paper is gospel to ''experienced pilots'', but to 45 hrs ppl's it probably sounds like chineese. You just cant expect pilots to understand in a few months what took nearly a century to come up with. But keep em coming.

[Colonel Sanders]

Ok. I'll take another swing at it.

You know what "G" is, right? Sitting in your
chair, you're experiencing +1G. In a steep
turn, you can experience +2, +3 or +4G.

You can also decrease the G, too, by gently
pushing forward on the control column.

Here's the one fact I want you to learn:

Vs(G) = sqrt(G) x Vs(1G)

You can derive it from the lift equation. It
tells you the relationship between G and
stall speed.

At +2G, your stall speed increases 1.4x
At +4G, your stall speed increases 2x

And at 0G, your stall speed is ZERO. This
is because you aren't asking the wings to
produce any lift, so they can't stall.

Think of the airplane, parked in the hangar.
Airspeed is zero, but the stall warning isn't
going, because you aren't asking the wings
to produce any lift. The landing gear are
doing all the work.

If you can spend the time to read and re-read
the above until you understand it, you are
a long way along the journey of actually
understanding the theory of flight.

Like the above? Keep reading, here:

www.pittspecials.com/articles.html