POH/AFM Book Values Are Full Of Shit

[Colonel]

I can't believe I'm having to post this, but apparently people are
believing the bullshit written by aircraft salesman.

Let's take a simple example:  a Cessna 172M:

[img width=500 height=226][/img]

The salesmen at Cessna say that a shiny new 172M at max gross and approached
at 70 mph, will have a ground roll of 520 feet (sea level, ISA, paved runway, no headwind).

What bullshit.  You can try all sort of desperate stuff after touchdown like
grabbing for the flap handle - that's going to work out really well for you later, in
retractable gear aircraft - and locking up the brakes and flat-spotting the mains.

I would wager that not one [u]flight instructor[/u] in Canada could duplicate Cessna's
number of 520 feet at max gross in their tired old POS 172.

Now, let's look at what the Cessna salesmen have to say about crosswind landings.

[img width=500 height=61][/img]

Fucking hilarious.  "Average Pilot Technique" is what you need for a direct 15 knot
crosswind?  You'd have to be pretty stupid to believe that.  Show me a PPL that can
handle a direct 15 knot crosswind in a 172.  Fuck, I've seen fresh CPL's from the local
puppy mill that can't handle 5 knots of crosswind in a 172.

Please don't believe that flight manual nonsense.  Apparently some people do, which
is going to cause accidents.  Not sure if you give a shit or not, about whether or not
you have an accident.

[Slick Goodlin]

It’s been a while since I flew a 172M but... can’t they?  I suspect the chart cheats a little; nowhere does it say max gross, and I bet while they may have flown the approach at 70 the touchdown was substantially slower.

Now I just want to borrow a Cessna and see what I can do with it.

[David MacRay]

I like trying to make the first taxiway without brakes or stunts. How far that is depends on which runway is active where I very occasionally fly. I was pretty decent at cross winds because when I was flying around Okatoks there was only one runway. Cross wind was pretty much a given there.

[Colonel]

Max gross is 2300 lbs (see the left column) in the 172M with 40 flap.

I guarantee you, if you approach at 70 mph at 2300 lbs as per the book,
you cannot get it stopped in the book distance of 520 feet.  #fakenews

...unless you employ the special "TC Technique":

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


As far the 15 knot direct crosswind "average pilot" nonsense ... that is
so ludicrous, it doesn't even merit a response.

Free advice:  apply a correction factor of x2 to the flight manual "fantasy numbers".

For example, 520 x2 = 1040 feet to land a 172M at max gross

15 knots / x2 = 7.5 knots direct crosswind for average pilot

I only have 1000 hours in 172 - at trial, Arlo bragged he had far more than I -
but that's what my experience tells me.

[Slick Goodlin]

...then at some point the marketing department stopped writing the manuals and the legal department took the reins.  I’m not going to look, but a 172S manual probably gives three times that distance.

[Colonel]

Between the salesmen and the lawyers, it's a fluke if any information
about the product actually makes it from the company engineers to
the end users.

[Colonel]

Short field landings on really long paved runways always struck
me as a complete waste of time, and a great way to flat-spot the
tires.  I know TC loves them, but ...

When I was still allowed to hold an instructor rating, I used to use
a parallel grass strip which I mowed myself.  Get the student to nail
the airspeed.  First 70, then 65, then 60 mph on short final, landing
on the long paved certified runway.  No obstacles.

Then, sidestep to the grass strip, and get him to plop it onto the
grass with 60 mph on short final.  I didn't encourage the student
using braking, because it didn't do anything on grass.  I didn't let
him fuck with the flaps, because that's dangerous and doesn't help.

It really didn't matter what the light aircraft type was.  If you could indicate
60 mph on short final, and plop it down onto the same spot on the grass,
you would use about 500 feet rolling out.  This was pretty much sea level
ISA with negligible wind.  See "kinetic energy".

That seemed to me, to be a pretty useful exercise for an advanced
student pilot.  Rather than trying to lock the brakes up on the pavement,
which just made me cry.  Tires are fucking expensive.  Don't teach the
student to be grabbing levers inside the cockpit during the fucking rollout.

Jesus Christ.

[John Swallow]

The poor old RV pointing at the ground was not the result of a botched landing.  AAMOF, the landing was perfect.  The rollout was something else...

[Colonel]

I knew there was a trick to your short landing distances

#TCInspectorsHaveMagicPowers

In my 45 years of flying, I have observed that your
landing distance is determined as much by what you
do before touchdown, rather than the frantic actions
in the cockpit after touchdown.

A wise pilot gets rid of his kinetic energy before
touchdown by slowing down to the safest speed
possible over the threshold, and touching down
on the numbers.

Despite what TC tells you, you don’t need to drag
it in at that slow speed, starting at 1000 AGL or
whatever.  The only things that matter are where
you touch down, and how fast you are going at
that instant.

Oh yeah, please don’t fish for a greaser, for many
reasons.  Set it down firmly.  But not on it’s nose.

[John Swallow]

"A wise pilot gets rid of his kinetic energy before touchdown by slowing down to the safest speed possible over the threshold, and touching down on the numbers."


Concur.  [color=rgb(91, 91, 91)][/color]