Impossible Turn

[Colonel]

Everyone will tell you that it is impossible to
turn back, in a little single, after engine failure
after takeoff, and land on the same runway you
took off on, in the opposite direction.

While this is terribly egalitarian, and levels
everyone down, it isn't actually true.

See, [u]what the airframe is capable o[/u]f, and
[u]what the pilot is capable of[/u], are very different. 

The [u]pilot's abilities are almost always a subset
of the aircraft's capabilties[/u].  Few pilots are
capable of flying precisely to the limit of an
aircraft's performance, defined as being the
border of the Vg diagram. 

[img]https://www.metabunk.org/data/MetaMirro ... 36077e.jpg[/img]

In Canada, there's Pete MacLeod and that's about
it.  Maybe Gerry Younger, but he's really old.  No
one else can repeatedly and precisely fly an aircraft
around all the edges of that Vg diagram.

A turnback actually isn't very hard or dangerous,
with just a little bit of theory and training.

Most people think you're going to die in
power-off steep turn, and that's because
they are too lazy or stupid to learn about
the basics of lift.

All aerobatics pilots learn that your stall
speed is a function of G. 

No one cares, but the governing equation,
which is easily derived from the lift equation is:

[b]Vs(G) = Vs(1G) x sqrt(G)[/b]

Ask any TC Inspector to derive that on
the back of any envelope at lunch.  I
will happily do so, if you buy lunch.

With +4G, your stall speed is doubled.
Look at any Vg diagram to confirm that.

[b]But with 0G, your stall speed is zero.[/b]

Think about that.  This is true in any
aircraft.  If you don't pull any G with
the wings, no lift is developed and
there is no AOA.

In the EFATO turnback, you will have a
lot of bank - I use 60 degrees, see Prof
Dave Rogers USNA, 1991 - but you let the
nose drop and [b]don't pull any G[/b]. 

If you do what I say - and few do - you
won't stall.  Your AOA will be quite low,
because you aren't working the wing hard
in the turn.  You aren't asking it to make
any lift.

Any proficient aerobatic pilot will easily
perform the power-off descending steep
turn and point back at the runway.  Easy.

But here's the hard part: [b]making the departure
end of the runway![/b]

See, [b]most airplanes glide power-off at a steeper
angle than they climb[/b].  Re-read that.

So, if you have a short runway, no headwind,
and a shallow climbout, you might not make
it back to the runway.

However, if you have a long runway, some
headwind (tailwind on the return) and a steep
climbout, you can make the runway.

Oh yeah, always turn into the crosswind.  Don't
just turn left all the time, ok?

So on takeoff, you climb steeply and when the
engine burps, immediately crank the aileron all
the way over into the crosswind and [b]let the nose
drop[/b].  Trim selection can help here.  If you haul
back in the turn, bad things can happen.  Soft hands.

Most people like to practice it at altitude.  Ok.

With some instruction, training, practice and
preparation, this really isn't so hard.  I can do
this and eat a sandwich at the same time, and
I'm not too bright, so I'm sure any four bars
can do it.  Ask them to show you.

[ScudRunner-d95]

I witnessed one of those advanced ultra light type planes do such a maneuver (sort of)


For those familiar with Delta Airpark the aircraft departed on 07 towards the barn, and an altitude of about 600 feet AGL and maybe a quarter mile past the barn I saw him bank abruptly and turn for the field touching down about half way down the runway.


Turned out his engine wasn't fully Kaput it was still making some power at least enough to get him back to the ground. Some adjustments and I believe a bit of misplaced lock wire later he was good to go. Which brings me to my point, engines don't always go worst case bang and thats it.


note my signature

[Colonel]

Most of the time, it's just no fuel getting to the engine.

After all, don't gliders practice rope breaks and turnbacks?

;D

[Slick Goodlin]

I get the theory behind it and can wrap my head around the optimum speeds for it all but the singles I fly all suck at climbing.  They're even worse at gliding.  Knowing this (and it's alluded to above) I've always added that it's worth thinking about the landing area you're passing up on when you attempt the turn back for the field.  If there are endless flat and short crops in front of you, just go straight.

[Slick Goodlin]

[quote author=Colonel Sanders link=topic=6766.msg18369#msg18369 date=1501039955]
In Canada, there's Pete MacLeod and that's about
it.  [b]Maybe Gerry Younger[/b], but he's really old.  No
one else can repeatedly and precisely fly an aircraft
around all the edges of that Vg diagram.
[/quote]
IIRC my dad witnessed him do it in Kitchener back when Gerry had the Extra.  The kicker was he did it at surface level...  [i]inverted[/i].  Luckily he had built up lots of energy for what I assume was going to be a push to vertical (it was back when he really beat himself up - not unusual to see him afterwards with bloodshot eyes) and I imagine the Extra was a pretty slippery plane so it held onto that energy long enough to turn around and roll to upright before landing.


I always wished I had done some acro training with him but he's retired now and the planes all sold.  At least I did my tailwheel in his green clip wing Cub.

[DeflectionShot]

[quote]With some instruction, training, practice and
preparation, this really isn't so hard. [/quote]

Very interesting stuff. Thanks for this Colonel. I will be sure to ask my local Class One if we can practice this.  >:D

[Colonel]

Jesus, be careful.

Free advice:  [b]learn the theory[/b].  Few pilots do.

If you learn the underlying physics, you are at
an enormous advantage.  You can completely
ignore the silly rules that everyone else adheres
to, in a feeble attempt to live within a subset
of the math & physics.

This will get you into terrible trouble with
bureaucrats, but hey, they hated Bob Hoover, too.

[b]Keep the metal happy.  Keep the wing happy.[/b]

Airspeed is a shitty proxy for AOA.  The wing
could not care less about airspeed, or bank
angle.  It has no eyeballs.  The wing does not
see the ASI or the horizon, and become scared.

[b]The wing only cares about AOA.[/b]

Pilots care about airspeed and bank angle.  The
wing does not.  I give a shit about the wing, not
what other pilots think.  This leads to [i]hurt feelings[/i]
but oh well.

[b]Vs(G) = Vs(1G) x sqrt(G)[/b]

learn that equation well.  Half of the Vg diagram
is derived from it!

Physics is applied mathematics.
Engineering is applied physics.

Those two sentences will teach you more about
aviation than 100 pages of [u]From The Ground Up[/u].


PS  Gerry Younger was an awesome pilot 20
years ago, when he was only 65  ;D 

When you're 80 or 90, it's really hard to be as
sharp as when you were 20 or 30.

[img width=500 height=250][/img]

[Chuck Ellsworth]

Good post Colonel.


However I worry that some pilots will attempt to teach them self without enough altitude to recover if they lose control of it.


I wonder how many flight instructors understand how an airplane really fly's?


Someone should go over to Avcanada and ask B.P.F. what his opinion is about the turn back after take off now that he is at T.C.

[vanNostrum]

On average, what would be the minimum height to attempt the manoeuvre? [C172]

[cgzro]

Did a lot of aerobatic and tail wheel with Gerry in Pitts C-GQSI in the early 2000s and he also ferried my Pitts up from Florida for me.


Saw him fly that Extra 300S at surface from the intersection of the runways at Kitchener Waterloo one day, incredibly impressive and I've not seen a [u]solo[/u] low level routine as good and as skillful as Gerry's in Canada since. He started with a roll to inverted then a midfield rolling spiralling climb , transition seamlessly to a torque roll to a tail slide wheels up and come right back down the runway inverted. It was both beautiful and very very difficult to do.


A very demanding instructor.