preparing for commercial oral and practical

Mark T. Dame wrote:
For both my private and commercial rides I was required to do a W&B for
takeoff and landing fuel loads. Additionally, for my commercial ride, I
had to account for the gear position, as Matt said, giving you four
different configurations.

This was another point of emphasis for my DE. Different examiners have
different favorite topics. For the purpose of the original question, my
suggestion stands.

I'm not questioning your experience, just relaying mine.


My private and instrument rides were with a retired USAF type popularly locally
known as Colonel Goddammit. I also did some of my single and multi 135
checkrides with him. He had his quirks to be sure and God help you if you
attracted his attention. First his fingers would start tapping his legs, faster
and faster until finally the blast would come, blistering the side of your face.
You'd be deaf in one ear and your hair would look like you'd been riding a
motorcycle... sideways. Sometimes I'd **** up intentionally just to get it over
with.

My commercial checkride was with a more mellow character who was a DE, former
chief pilot for a commuter, and current chief pilot for a high priced charter
outfit.

Multiengine checkride was with a similar type associated with one of those
weekend multi schools.

Later 135 rides were with an airline captain who owned a courier service on the
side and with a longtime freight dog chief pilot.

I never had to do W&B in more than one configuration my entire flying career.
Frankly, until I read the OP's note a couple of days ago, I'd never heard of
this being done. Now it's my turn to say: I'm not doubting your experience;
it's just very different from mine. Could it be this is one of those quirks
courtesy of somebody at your local FSDO who focuses on this as a way to trip
people up?



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

Mark T. Dame wrote:


Additionally, you do have the gear in both positions in flight. You
have it down at take off. You need to make sure that putting it up
isn't going to put your CG outside of the envelope right after take off
when you are still low, slow, and nose high. This could lead to a
departure stall. When you are landing, you put your gear down well
before you touch down, and you will be low and slow on final. The
difference between gear up and down may be a factor.

Bull****. Somebody mentioned that the gear will make a 1/2" difference
in CG. I personally don't believe that, it's way too much. But
assuming it's true no airplane falls out of the sky by going from the CG
on the aft limit to 1/2" past the aft limit.

Mortimer Schnerd, RN wrote:

My private and instrument rides were with a retired USAF type popularly locally
known as Colonel Goddammit.

Talk about unneeded pressure on a checkride...


I never had to do W&B in more than one configuration my entire flying career.
Frankly, until I read the OP's note a couple of days ago, I'd never heard of
this being done.

Which just goes to show, even though we all fly by the same regulations,
things are not always the same. You can see those differences even from
FBO to FBO in the same area.


Could it be this is one of those quirks
courtesy of somebody at your local FSDO who focuses on this as a way to trip
people up?

Possibly, but I would put my money on the DE. She has her own ideas
about what's important and what's not. She also tends to be pretty
thorough, but like most DE's she has her favorite things. My CFI (who
had done his commercial checkride with her a couple of years earlier)
gave me a list of things that I absolutely had to have ready. I don't
recall the entire list, but the W&B with both gear configurations was
one of them.


-m
--
## Mark T. Dame
## CP-ASEL, AGI
## insert tail number here
## KHAO, KISZ
"There is a theory which states that if ever anyone discovers
exactly what the Universe is for and why it is here, it will
instantly disappear and be replaced by something even more bizarre
and inexplicable.

There is another which states that this has already happened."
-- The Restaurant at the End of the Universe, Douglas Adams

Newps wrote:


Bull****. Somebody mentioned that the gear will make a 1/2" difference
in CG. I personally don't believe that, it's way too much.

You don't have to believe it. If it's in the book, that's what you use.
It's not a matter of opinion. It is what it is.


But
assuming it's true no airplane falls out of the sky by going from the CG
on the aft limit to 1/2" past the aft limit.

No it doesn't. It affects the stability, the stall speed, and the
ability to recover from a stall. In an Arrow, I don't think it will
matter a hill of beans, but in a Cutlass, it might.

But the point of the conversation is preparing for the commercial
checkride, not whether or not raising the gear on a specific model of
airplane will move the CG too far aft for safe operation.


-m
--
## Mark T. Dame
## CP-ASEL, AGI
## insert tail number here
## KHAO, KISZ
"Help stamp out and abolish redundancy!"

Somebody mentioned that the gear will make a 1/2" difference in CG. I personally don't believe that, it's way too much.

I showed the calculation. It's in the Arrow book.

But assuming it's true no airplane falls out of the sky by going from the CG on the aft limit to 1/2" past the aft limit.

No, but with thinking like that, if you decided to fly an inch out of CG
and ended up an inch and a half...

Jose
--
Quantum Mechanics is like this: God =does= play dice with the universe,
except there's no God, and there's no dice. And maybe there's no universe.
for Email, make the obvious change in the address.

Most of the DE's that I've encountered have a certain amount of "teacher" in
them that is very often only slightly contained. I feel that the DE's who
ask about CG changes with gear movement are trying to teach more than
torture a student the fact that you don't necessarily have to move people,
baggage, cargo, or fuel to have a CG change. Sometimes, depending on the
airplane ( and you are preparing to fly bigger and more complex airplanes)
an aircraft's CG will change due to a normal flight operation, such as
extending or retracting the gear.

I don't think the magnitude of the CG change that is the emphasis of the
DE's questions or teachings, rather the fact that it can change. I think
this lesson is meant to point out the importance of a complete understanding
of W&B as applied to each particular aircraft using the proper W&B and POH
information.

Jim

Mortimer Schnerd, RN wrote:
Mark T. Dame wrote:
For both my private and commercial rides I was required to do a W&B for
takeoff and landing fuel loads. Additionally, for my commercial ride, I
had to account for the gear position, as Matt said, giving you four
different configurations.

This was another point of emphasis for my DE. Different examiners have
different favorite topics. For the purpose of the original question, my
suggestion stands.

I'm not questioning your experience, just relaying mine.


My private and instrument rides were with a retired USAF type popularly locally
known as Colonel Goddammit. I also did some of my single and multi 135
checkrides with him. He had his quirks to be sure and God help you if you
attracted his attention. First his fingers would start tapping his legs, faster
and faster until finally the blast would come, blistering the side of your face.
You'd be deaf in one ear and your hair would look like you'd been riding a
motorcycle... sideways. Sometimes I'd **** up intentionally just to get it over
with.

My commercial checkride was with a more mellow character who was a DE, former
chief pilot for a commuter, and current chief pilot for a high priced charter
outfit.

Multiengine checkride was with a similar type associated with one of those
weekend multi schools.

Later 135 rides were with an airline captain who owned a courier service on the
side and with a longtime freight dog chief pilot.

I never had to do W&B in more than one configuration my entire flying career.
Frankly, until I read the OP's note a couple of days ago, I'd never heard of
this being done. Now it's my turn to say: I'm not doubting your experience;
it's just very different from mine. Could it be this is one of those quirks
courtesy of somebody at your local FSDO who focuses on this as a way to trip
people up?

I think it is just different DEs checking different things. To me W&B
is one of the things you don't skip as discretionary. Much of the stuff
covered on a check ride is stuff that won't kill you if you don't know
all of the details. Things like what every stinkin antenna on the
airplane is for. I can count on zero fingers the number of times in 30
years of flying that I had to know that to save my life. OTOH, if you
take off at the aft CG limit and retracting the gear puts you 1/2" or so
past the aft limit, this has the potential to kill you. Same with fuel
burn. If you have an airplane that shifts CG aft with fuel burn, this
can cook your goose later in the flight.

Violating rules of the FAA is one thing, but trying to violate the rules
of physics is quite another.

Matt

Mark T. Dame wrote:
Jose wrote:
Now, as Jose pointed out, on the Arrow it's not very significant

Actually I wasn't implying (half an inch) that it wasn't very
significant - when the CG range is only a handful of inches, it's
significant. And certainly when you're near the edge it bears watching.

At the risk of arguing semantics, I wasn't saying "insignificant" only
"not very significant". I don't have my Arrow book here, but I believe
the CG range is around 10 to 12 inches. If you load well within the
envelope, the half inch is not going to have an appreciable affect on
aircraft performance.

But I'm getting off topic: what should someone expect on their
commercial checkride.

Make sure to do a W&B for gear up and gear down with takeoff fuel and
landing fuel. If the examiner doesn't care, then no big deal, but if
the examiner wants to see it and you didn't do it, then you have a
strike against you. On checkrides, you'll get plenty of strikes without
creating ones that could be easily avoided by a little bit of prep work.

Even if the examiner doesn't want or expect it, it can't hurt to have it
(unless you do it wrong).

Yes, and it is also just good operating practice, check ride or no. I
have it in my spreadsheet so that it calculates both CG locations and
all I have to do is enter the fuel expected at takeoff and at landing.

Balance isn't something to be taken lightly. Being 200 lbs over gross
typically isn't a big deal (I'm NOT recommending it), but being an inch
aft of the CG limit can be fatal.


Matt

Jose wrote:
Somebody mentioned that the gear will make a 1/2" difference in CG. I
personally don't believe that, it's way too much.

I showed the calculation. It's in the Arrow book.

But assuming it's true no airplane falls out of the sky by going from
the CG on the aft limit to 1/2" past the aft limit.

No, but with thinking like that, if you decided to fly an inch out of CG
and ended up an inch and a half...

I don't see a half inch of change, but it is still a fair amount
(0.34"). Here is my spreadsheet calculation from my last flight.
Unfortunately, the formating from Excel gets hosed pretty badly.

The point is that nobody knows for sure how far past the aft limit is
too far for any given flight condition and operating past the aft limit
at all is just dumb. The only thing dumber is not even knowing that you
are aft of the limit.

Matt

Piper Arrow PA28R-3009 N3705T

Quantity Weight Arm Moment
Airplane empty 1552.65 84.53 131253.15
Oil 15.00 29.50 442.50
Fuel 50 300.00 95.00 28500.00
Pilot and front seat passenger 385.00 85.50 32917.50
Rear passengers 125.00 118.10 14762.50
Baggage 30.00 142.80 4284.00
Gear retraction 819
2407.65 88.11897493 212159.65 Gear down
88.45914066 212978.65 Gear up
Gross Weight (2500 max) Center of Gravity Total Moment

"Mark T. Dame" wrote in message
...
Newps wrote:


Bull****. Somebody mentioned that the gear will make a 1/2" difference
in CG. I personally don't believe that, it's way too much.

You don't have to believe it. If it's in the book, that's what you use.
It's not a matter of opinion. It is what it is.

The POH for this PA-28R has "Moment due to retracting landing gear = +819
in-lbs" beneath the CG Range and Weight Chart, so I'm going to plan
accordingly for the exam. Thanks for the heads up!

-c