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Why Tailwheel?

Posted: Sat Aug 24, 2019 10:20 pm
by Colonel
It's a good question.  At the end of WWII, the writing was on the wall.  The Germans first made
a taildragger jet, then realized that was silly, and it was nosewheel from then on.

A taildragger simply has it's Center of Mass aft of the main gear, so that on the ramp, the tail
is on the ground, with a troublesome little wheel there.  More about that later.

A nosewheel aircraft just has it's Center of Mass ahead of the main gear, so that on the ramp,
the nose is on the ground, supported by a large, ugly, shimmy-prone nosewheel.

I'm actually not much of a fan of either tailwheels or nosewheels, as you might notice.  Like
going to the dentist or proctologist, both are going to cause you pain, sooner or later.

[img width=500 height=281][/img]

A taildragger, when the tires are on the pavement, is directionally unstable.  An accident
waiting to happen.  All that prevents it, are the pilots feet.  The reason for this is if it gets
an angle, the center of mass behind the main gear pushing forward makes the angle
worse, and off the runway you go.  This is more of a problem during landing, than taking
off, when the thrust from the prop helps straighten you out, and less than incidentally, blows
air over the vertical fin and rudder, increasing their authority.  But pilot still manage to come
to grief on takeoff in a taildragger.

A nosewheel aircraft, when it tires are on the pavement, is directionally stable.  If it gets
an angle, the center of mass ahead of the mains will help straighten it out.  You may note
that the pre-WWII P-38 was a nosewheel aircraft.  Kelly Johnson was no dummy.

This begs the question:  why on earth would anyone build a taildragger?  People mumble
that they are one mph faster because of the smaller tailwheel vs nosewheel, but that's
nonsense.  Subjectively, they might look better.

The reason for a taildragger is merely prop clearance on the ground.  With the same prop
diameter, you have more prop clearance than a nosedragger, which is nice for rough field
ops.  People will mention that the C206 sees plenty of rough strips, though.

However, being able to increase the prop diameter on a taildragger can yield enormous
benefits in terms of resulting thrust.  Remember, the prop on an aircraft is the transmission,
driveshaft, differential and tires on a car - it does all the work of transmitting the horsepower
from the crankshaft to the world outside.

I have flown the 195cm MT on the Pitts S-2B, and it sucked moose cocks.  And I have flown
the 206cm MT on the Pitts S-2B, and it's a very good, cheap prop.  Much better than the 195.

Only 9 cm of diameter, or 4.5 cm of radius, or less than two inches makes a world of difference.
If you don't believe me, ask your girlfriend if she would notice another two inches.

The composition of the prop blades on a taildragger is enormously important.  No one will tell
you this, but two - or God help you, three - metal blade prop(s) will make your life interesting
in a taildragger.  Tail goes up, nose goes left.  Tail goes down, nose goes right.  This "coupling"
of pitch and yaw may or may not be controllable.  Best to pitch tail up and tail down very slowly,
with a metal blade prop on a taildragger.  Beech 18 comes to mind. 

[img width=500 height=332][/img]

However, with a wood or composite blade prop, this almost disappears, and you won't break
your crankshaft during aerobatics, which is a nice plus.

[img width=500 height=297][/img]

Let's talk about a taildragger takeoff.  You line up on the runway, and smoothly apply full power.

At this point, there are three things you can do:
(1) keep the tailwheel on the ground until you take off
(2) slightly raise the tailwheel with a little forward stick
(3) get that fucking tail all the way up with lots of forward stick

(2) & (3) are actually minor variations of the same theme - raise the tail.  Most people go for (2)
but it looks sucky.  Go for (3), keeping in the mind the slow pitch change if you have a metal
blade prop, to avoid needing genius footwork.

(1) is what we use for rough and soft field takeoff.  Gerry Younger actually recommends it in
the Pitts S-2A, and I've had to resort to it, teaching on the Christen Eagle, but it's high drag
and you pop into the air at a very slow speed, requiring genius work with the stick to pitch
down - without a PIO - to stay in ground effect and accelerate to a safe speed, until you
climb out.  That takes a lot of practice, so I would only recommend this technique in an
aircraft with entirely too much power, or far too little prop clearance.

Once you're in the air, you can relax.  A taildragger flies just the same as a nosewheel
aircraft, once the tires are no longer touching dry pavement.

Or is it?  Looking at a taildragger, there are signs to look out for.  If it's got a short
fuselage and a small vertical fin, it will may have very little directional stability even
in the air.  The original Maule M4-210C that's been in the family for decades is like
that.  The ball has no tendency whatsoever to stay near the center.  Later Maules
have massive vertical fins, which help with stability, but really weathervane in a
crosswind.  Given the choice, I'll take the small vertical fin.

[img width=500 height=375][/img]

And that brings us, in my incredibly indirect and meandering way, to the reason
why you should fly a taildragger:

LEARN TO CONTROL YAW

That sure sounds simple, doesn't it?  A taildragger is completely unforgiving of
a pilot that cannot use his feet to control yaw.

In a perfect world, every pilot would do his first 10 hours of training and solo in
a taildragger.  The lessons - the instincts - he learned would last a lifetime.

It takes twice as long to teach someone to fly tailwheel, if they have been flying
nosewheel, and learned that they don't need to use their feet.  They need to learn
new instincts, and that takes time.

Now, let's talk about tailwheel landings, which is what most people whine about
the most.  First, when you are starting out, tanker fuel.  I want to see full tanks,
every takeoff.  That fuel gives you time.  Bad shit happens when people don't
have time.  Stack the deck in your favor.

One final, learn to precisely control your airspeed.  Figure out what it should be,
and nail it.  Get on the centerline and 3 degree glide path.  Aim to touch down
on the numbers.  Reduce power to idle over the threshold.

If the aircraft has flaps, I recommend setting them for takeoff, because when
it's time to overshoot, you don't want to put your head down, going from land
flap to takeoff flap.  Make it easy on yourself.  If the aircraft specifies no flap
for takeoff - or has no flaps - there's your answer.

Try to not get behind the aircraft in the flare.  Most people do, and flare too
quickly, too low.  This pitchup yaws the aircraft right, and we touch down
with an angle.

Sigh.  I have seen this, thousands of times.  There is ONE THING you
need to remember about a taildragger landing:

NO CRAB

The aircraft MUST touch down with no yaw angle, with respect to the
direction of travel.  If you do that, it is not stable, but if the aircraft is not
damaged - many are - it will continue to roll down the runway with no
input from the pilot.  Fucking magic.  Like a piston balanced at the TDC
with 80 psi - hands off.

You never, ever force a taildragger onto the ground, unless it is on fire.

If you ask yourself, "Should I go around?" the throttle goes all the way
in.  A friend of mine - he in prison right now - got a Pitts S-1C and he
would do 10 approaches until he got one that he liked.  I approved of
that, even if I didn't particularly approve of what he did, to get locked up.

A good approach should lead to a good flare which should lead to a
good touchdown which should lead to a good rollout.

If ANY of the above are not aces, overshoot.  You've got lots of fuel,
remember?  It takes a LOT of experience and skill, to force a bad
approach into a good flare, or a bad flare into a good touchdown, etc.

Now, for the actual landing.  Perfect technique is putting the aircraft
in the landing attitude, with all tires 6 inches above the pavement, with
the power off.

[img width=500 height=306][/img]

That's what 10,000 landings looks like.  As the used car salesman with
the hair piece from Dallas says, go out and Get You Some Of That.

Make sure your idle isn't set too high.  Fucking AME's will set it much
too high at annual.  With the engine warm, I want to see 650 RPM, no
more.  Even another 200 RPM really extends the touchdown, and gives
BAD THINGS more time to happen.

One trick I use with my Maule, because the only people who fly it share
my Y chromosome and are fucking awesome sticks, is to set the idle so
low that if you pull the throttle back on the ground, the engine quits.

This sounds insane, but stick with me.  On final, that constant speed prop
provides IMMENSE and controllable drag with the idle set so low, with the
prop driving the engine.  Don't do that with a geared engine, of course.

The drag during the touchdown decelerates the aircraft very quickly out
of the "expensive speed" which I define as 20 to 40 mph.  Below 20 mph
you are taxiing.  In the expensive speed range you are neither flying or
taxiing, and small errors are expensive.

Above is the famous "three point" landing, which works well in light aircraft
with good tailwheels that don't shimmy.  Some people prefer wheel landings,
which generally require more airspeed to reduce alpha, and that's fine.  Like
boxers vs tight whities, no one can tell you what feels best for you.

But, what I have observed is that there is a spectrum.  Very light, slow aircraft
respond very well to three point landings.  But very heavy, fast aircraft respond
better to wheel landings.  In between, well, do what works for you.

The neat thing about a taildragger is that you can wheel it on, at tremendous
speeds that you would never dream of in a nosewheel aircraft.  A good example
is landing out of a loop.  I rather liked doing that at airshows in Central America.

Remember I mentioned a genius called Kelly Johnson earlier?  Well, he also
designed the U-2 - basically an F-104 fuselage with glider wings - and made it
a taildragger.  Kelly Johnson had a sense of humor, evidently:



I approve.

Now, you quite reasonably might opine that you don't care about taildraggers,
and you're never going to fly the U-2, so does it matter?

Sure does.  Recently, two different King Air accidents - Vmc demos with the
trademark inverted landing - have shown the value of a pilot who

LEARNS TO CONTROL YAW

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This is what happens when a nosewheel pilot tries to control yaw:



Once you can control yaw, crosswind landings are something you look forward to:


Re: Why Tailwheel?

Posted: Sun Aug 25, 2019 12:57 am
by Chuck Ellsworth
Looks are subjective for sure.

I am in he process of building a Thatcher CX4.

Compared to the CX5 there is no contest for looks.

The most difficult to control on ground tail wheel airplane I ever flew was the Turbo Goose.

The easiest was the DC3.

Re: Why Tailwheel?

Posted: Sun Aug 25, 2019 5:05 am
by Colonel
I have few regrets in life, but one of them is that I never got a
C-46 type rating.  I would gladly give your left nut to fly that pig.

PS  Note the use of pictures and videos in my postings.  I understand
this upsets the white-shirt crowd.  Message to white shirts: 

Suck it up, buttercups, and try to keep it on the black stuff between the grass.

Re: Why Tailwheel?

Posted: Tue Sep 03, 2019 9:24 pm
by digits
[quote author=Colonel Sanders link=topic=9982.msg28628#msg28628 date=1566685233]
You never, ever force a taildragger onto the ground, unless it is on fire.
[/quote]

This seems to imply that forcing a tailwheel airplane down is worse than forcing a nosewheel airplane down. Why is that?

I'd expect a tailwheel plane to be more resistant to damage when forced down. If you force a nosewheel down, chances are you'll be porpoising untill the nosewheel breaks.

To clarify, I wouldn't advocate forcing any airplane on the ground, but curious why you put that sentence in there.

Re: Why Tailwheel?

Posted: Wed Sep 04, 2019 12:49 am
by Colonel
Both nosedraggers and taildraggers can bounce horrifically.

That is something to avoid.  I think I said later in the post that
yes, you can put a taildragger on the ground at tremendous
speed - but it must be done carefully.  Yeah, here it is:

[quote]The neat thing about a taildragger is that you can wheel it on, at tremendous
speeds that you would never dream of in a nosewheel aircraft.  A good example
is landing out of a loop.  I rather liked doing that at airshows in Central America.[/quote]

Landing out of a loop at the surface, in the yellow arc with the tail
'way up in the air, is really something best left for the experts.

No crab, and you kiss it on sooo gently, like kissing a porcupine.

The nice thing about landing a taildragger in the yellow arc on the
ASI, is that you can finally see something forward!

Hey, did I mention the trick for a good, normal wheel landing?  I'm
sure I've mentioned it before, but ... even with no crosswind, at the
last moment, sideslip before touchdown.  If you don't get a greaser,
instead of the tail coming down, the other main comes down.  A little
forward stick and both mains are stuck, with the tail up in the air, and
the stick continues to move forward as you slow down, until it's all
the way forward, and you gently lower the tail.

Re: Why Tailwheel?

Posted: Wed Sep 04, 2019 11:37 am
by cgzro
[quote]
Hey, did I mention the trick for a good, normal wheel landing?  I'm
sure I've mentioned it before, but ... even with no crosswind, at the
last moment, sideslip before touchdown.  If you don't get a greaser,
instead of the tail coming down, the other main comes down.  A little
forward stick and both mains are stuck, with the tail up in the air, and
the stick continues to move forward as you slow down, until it's all
the way forward, and you gently lower the tail.
[/quote]

I've been using this little bit of advice you gave for nearly 20 years and I try to pass it on when I can.

Re: Why Tailwheel?

Posted: Wed Sep 04, 2019 2:23 pm
by Liquid Charlie
It's interesting to watch how things change with time and the evolution of ideas and Technology. I started flying in an era where conventional gear was the norm. All initial training was started and completed with for me on trail daggers. The Chinese airforce at the island was likely the one place using C150's.

My first 10 years doing it for a living was also done in conventional geared aircraft, floats wheels and skis. We never needed a checkout to convert to tricycle gear. A lot of times not even a type checkout. If you flew a180/185 jumping into a 206 was a non issue. If you flew a Bch18 jumping into any light twin was just a matter of fact.

We are now into an age of the erosion of basic stick and rudder skills due to automation and social media. There has been a history of twisted metal and design flaws in jet airliners. Right from the comet to the present day Max. The difference is the era of social media has allowed the issue to approach the ridiculous. The fact that the crew was certainly a contributing factor people have chosen to ignore these facts. The era of fake news is entrenched in our lives. Look at the impact of the antivax group of idiots.

I think the MAX issue is more about training and experience than it is about the aircraft. Yes there are design concerns and certainly the misguided approach to training but airlines must also accept responsibility for lack of over sight. The Boeing training is a minimum and companies must access their own requirements and add to it as their situation dictates. I find it interesting the location of these max accidents. I'm sure similar failures have happened in north America and Europe and were obviously dealt with.

I can still remember listening to air Canada pilots complaining about the initial ground school in the 1011. These were dc8 drivers and before that Viscount and Vanguard. They couldn't get their head around the lack of requirement for system knowledge. This is the first of the present day computer based training and automation era. While I'm not a big fan of regurgitating system schematics from memory, I do think there needs to be an understanding of what is happening.

Unlike the Colonell most software engineers don't think like pilots so some of the logic behind the software is difficult to understand from a pilot's point of view. I can remember doing the initial factory coarse on the universal fms system and the first words out of the instructors mouth was this system was not designed by people who thought like pilots.

Boeing is certainly guilty of pushing the MAX possibly before it was completely ready but I'm sure in their minds the issues were manageable, combine that with the snake oil salesmen and you set yourself up for disaster. As I said before so many developing aircraft have had the same traffic results. It's gone from structural to software and pilot skills continue to erode due to automation.

Re: Why Tailwheel?

Posted: Wed Sep 04, 2019 2:40 pm
by Colonel
I'm sure I have greatly annoyed a large number of people with my continuous
[s]diatribe[/s] message over the decades, that there is NO SUBSTITUTE for:

1) basic aircraft handling skills
2) systems knowledge

Without that foundation, pilots are ill-equipped to deal with reality.  Bad things
will inevitably happen.

And yes, engineers are [i]horrible[/i] at user interface design.  So few engineers
actually understand their customers, and how their products are used.

You don't get a good product by tossing stuff over the wall.  You've got to eat
your own dog food.