Forward CG Experience

Recently we flew with a friend who weighs over 320 pounds. With he and I
in the front seat, and just Mary in the back, we were at the very forward
limits of the allowable CG. Thanks to the Pathfinder's 1400 pound useful
load, however, we were still 250 pounds under gross, even with full tanks --
but the teeter-totter was certainly pretty far to the "teeter" side.

I was contemplating this as we came in to land. Departure had felt normal,
but I figured the flare to land would be effected, so I carried a few extra
knots on final. I also figured that the wind -- 12, gusting to 18, but
right down the runway -- would help a little, too. I opted for two notches
of flaps.

As we crossed the numbers, I noticed things just didn't "feel" right.
Pulling back on the yoke was having very little effect as far as changing
the angle of attack, yet the speed was still bleeding off. This was weird,
but -- as it was all happening in the last few seconds, there wasn't much
else to do but add a touch of power and pull back some more.

We arrived firmly, in a flat attitude. The nosewheel and mains hit nearly
simultaneously, and the end result was more like a mush into the ground than
my usual "flare, chirp, chirp, settle...". It was surprisingly smooth, but
I realized that if I hadn't given that extra burst of power, and a firmer
yank on the yoke, we might well have landed on the nose gear, with possibly
expensive consequences.

Later, on the way home, with Mary as PIC and our friend in the back seat,
things were much improved. The added weight in the back actually helped to
balance our normally slightly nose-heavy (thanks to the six-cylinder
Lycoming O-540) plane, and Mary remarked that it landed more like our old
Warrior used to.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

In article zR5tb.196731$HS4.1666204@attbi_s01,
"Jay Honeck" wrote:

Recently we flew with a friend who weighs over 320 pounds. With he and I
in the front seat, and just Mary in the back, we were at the very forward
limits of the allowable CG. Thanks to the Pathfinder's 1400 pound useful
load, however, we were still 250 pounds under gross, even with full tanks --
but the teeter-totter was certainly pretty far to the "teeter" side.


Took a heavy friend and his tiny wife for glider flights once. He was
right on 250 lbs. Put him in the front seat of a Grob 103 (a model
famous for being nose heavy anyway). With the stick all the way back,
airspeed was 60 knots. You can bet I carried some extra speed on final.
His wife was 90 lbs. Bolted in the iron ballast plates and put a chute
on her. She was still a little under the front seat minimum. Flew her
that way since I knew the glider was a little forward CG from a repair.
That was the best that glider ever flew for me.

Now I have a little Stits homebuilt. It is somewhat forward CG solo. So,
I will have some bolt-in ballast for the rear. With anybody in the back
seat, it will be aft CG once a gallon or two of fuel burns. I will have
to add some ballast up front. The most useful ballast I can think of is
an electric starter.

On Fri, 14 Nov 2003 14:42:39 GMT, "Jay Honeck"
wrote:

Recently we flew with a friend who weighs over 320 pounds. With he and I
in the front seat, and just Mary in the back, we were at the very forward
limits of the allowable CG.

Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay, with your indulgence, a little military history that is on your
post's topic.

During the dark days following Pearl Harbor and the invasion of the
Phillipine Islands, a highly practical and inveterate ex Navy pilot
scrounger by the name of Paul (later called Pappy) Gunn ran a rough
house airline out of the Phillipines called PAL (Philipine Air Lines).
He his airplanes were requisitioned by the army and Pappy had various
hair raising flights and encounters with Japanese aircraft and anti
aircraft fire from both sides before he wound up in Australia and then
Port Moresby.

Cutting out a lot of his story, he ended up in charge of a provisional
transport squadron and offloaded some A-20's that had been assigned
him. He discovered that they had arrived without any machine guns.
His combat experience to date had convinced him of the need for a LOT
of forward fire power to keep the enemy's heads down on the run in to
the target so he began modifying them.

He plated over the bombardier's position and installed a row of four
50 caliber machine guns in the nose, plus two more in blisters
alongside the cockpit for a total of six forward firing machine guns.

With the machine guns, internal bracing and ammo cans and ammo, the
fully loaded A-20 was seriously nose heavy (you wondered when I'd get
to the subject?) His first takeoff, apparently wasn't. He could not
lift the nose to get airborn.

So he relocated the two machine guns in side blisters, moving them
back behind the cockpit.

At this time Gunn met up with George Kenney, who arrived in the
theater with a notion about low level attacks utilizing some parachute
equipped fragmentation bombs he'd developed, which would slow their
descent to allow the bomber to move out of danger from an explosion
once the bomb was dropped.

He saw what Gunn was doing and immediately liked the concept. He
yanked Pappy from his command in the transport squadron and placed him
in charge of modifying more attack bombers.

The A-20's were immediately extremely effective, but Pappy was unhappy
with their performance, feeling that he needed a bigger bomber with
more capacity. Enter the B-25 strafer.

I've got to stop, I could go on about this for a while longer. ;-)

Corky Scott

I've got to stop, I could go on about this for a while longer. ;-)

I've seen pictures of those B-25 ground-attack strafers. I imagine they
were the "A-10 Warthogs" of their day...

Thanks, Corky!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

In article zR5tb.196731$HS4.1666204@attbi_s01, Jay Honeck
wrote:

As we crossed the numbers, I noticed things just didn't "feel" right.
Pulling back on the yoke was having very little effect as far as changing
the angle of attack, yet the speed was still bleeding off. This was weird,
but -- as it was all happening in the last few seconds, there wasn't much
else to do but add a touch of power and pull back some more.

Subtract the weight of the fuel burned enroute and recalculate you W&B
and C/G.
Which way does the moment move? Fore or aft?

"Jay Honeck" wrote in message
news:zR5tb.196731$HS4.1666204@attbi_s01...
Recently we flew with a friend who weighs over 320 pounds. With he and I
in the front seat [...]

Argh! "With him and me in the front seat". Sorry, pet peeve.

Anyway, some comments:

* Wind only reduces groundspeed. It has no effect on control effectiveness
for a given airspeed.
* As you found, forward CG translates into increased drag, which means
airspeed drops off quicker than usual. You can either carry more airspeed
on final (scrubbing off to normal touchdown speed in the flare, but doing so
more quickly than normal) or you can use more power (using thrust to offset
the extra drag).

The only thing aft CG isn't good for is stability. Otherwise, it's a good
thing. I prefer to fly my airplane with the CG as far aft as practical (and
legal, of course).

Pete

Argh! "With him and me in the front seat". Sorry, pet peeve.

Ooooo. That *was* bad, wasn't it? :-) Sorry.

* Wind only reduces groundspeed. It has no effect on control
effectiveness
for a given airspeed.

Yes. I was trying to say that the wind would help with a gentle landing by
allowing a slower touch-down speed.

As I've told my son, don't listen to what I *say*, dang it, listen to what I
*MEAN*.
;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

On 2003-11-14 06:42:39 -0800, "Jay Honeck" said:

I opted for two notches of flaps.

That probably did a lot to help your landing. Flaps add a nose down pitching moment - something you don't really need with a forward CG.

We arrived firmly, in a flat attitude. The nosewheel and mains hit nearly
simultaneously, and the end result was more like a mush into the ground than
my usual "flare, chirp, chirp, settle...". It was surprisingly smooth, but
I realized that if I hadn't given that extra burst of power, and a firmer
yank on the yoke, we might well have landed on the nose gear, with possibly
expensive consequences.

Not necessarily. Sometimes, this is as good as it gets. I've had lots of nosewheel first arrivals in a Seneca (before I figured out the little flap trick). It's only a problem if you let it get out of hand by chasing the oscillation.

Hey, if you want a heavy friend to take flying, ballast and all that,
I'm available! :-) In the UK though...

I have 2 seats and 200hp so not much of a problem in my plane.
However I learned on a 172 as when I walked up first time to my
6ft 5" body builder instructor, he took one look at me, looked at
himself and said "We're going to need a bigger aeroplane"!

Grob 103. I can't even fit in the front and move the stick. I'm fine
in the back though...it's about the only glider I can fit in and
waggle the stick.

When I fly a T-tailed Arrow solo I have to a) watch how much fuel
I put in, and b) usually put a sandbag in the baggage compartment.
It still needs full back yoke to the stops on landing.

Paul

"Wallace Berry" wrote in message
...
In article zR5tb.196731$HS4.1666204@attbi_s01,
"Jay Honeck" wrote:

Recently we flew with a friend who weighs over 320 pounds.

Took a heavy friend and his tiny wife for glider flights once. He was
right on 250 lbs. Put him in the front seat of a Grob 103

It's my understanding that after Pappy Gunn had modified a B-25 for
straffing, with six 50 Cal Brownings in the nose and a 75mm field howitzer
under the floor of the cockpit, and had used it very successfully against
Japanese shipping, North American sent an engineer out to see what this
lunatic was doing. After looking over Gunn's field modification he just
shook his head and asked "Where the hell is the center of gravity?" Gunn
just shrugged and told him "Aw, we threw that out to save weight." The
engineer went home and North American started mass producing a properly
engineered variant of Gunn's cludge, the B-25G.

--
Bob (Chief Pilot, White Knuckle Airways)


"Corky Scott" wrote in message
...
On Fri, 14 Nov 2003 14:42:39 GMT, "Jay Honeck"
wrote:

Recently we flew with a friend who weighs over 320 pounds. With he and
I
in the front seat, and just Mary in the back, we were at the very forward
limits of the allowable CG.

Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay, with your indulgence, a little military history that is on your
post's topic.

During the dark days following Pearl Harbor and the invasion of the
Phillipine Islands, a highly practical and inveterate ex Navy pilot
scrounger by the name of Paul (later called Pappy) Gunn ran a rough
house airline out of the Phillipines called PAL (Philipine Air Lines).
He his airplanes were requisitioned by the army and Pappy had various
hair raising flights and encounters with Japanese aircraft and anti
aircraft fire from both sides before he wound up in Australia and then
Port Moresby.

Cutting out a lot of his story, he ended up in charge of a provisional
transport squadron and offloaded some A-20's that had been assigned
him. He discovered that they had arrived without any machine guns.
His combat experience to date had convinced him of the need for a LOT
of forward fire power to keep the enemy's heads down on the run in to
the target so he began modifying them.

He plated over the bombardier's position and installed a row of four
50 caliber machine guns in the nose, plus two more in blisters
alongside the cockpit for a total of six forward firing machine guns.

With the machine guns, internal bracing and ammo cans and ammo, the
fully loaded A-20 was seriously nose heavy (you wondered when I'd get
to the subject?) His first takeoff, apparently wasn't. He could not
lift the nose to get airborn.

So he relocated the two machine guns in side blisters, moving them
back behind the cockpit.

At this time Gunn met up with George Kenney, who arrived in the
theater with a notion about low level attacks utilizing some parachute
equipped fragmentation bombs he'd developed, which would slow their
descent to allow the bomber to move out of danger from an explosion
once the bomb was dropped.

He saw what Gunn was doing and immediately liked the concept. He
yanked Pappy from his command in the transport squadron and placed him
in charge of modifying more attack bombers.

The A-20's were immediately extremely effective, but Pappy was unhappy
with their performance, feeling that he needed a bigger bomber with
more capacity. Enter the B-25 strafer.

I've got to stop, I could go on about this for a while longer. ;-)

Corky Scott