Today's Message Index:
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1. 03:58 AM - Re: Landing a loaded RV-4 (Rob Ray)
2. 04:38 AM - Re: Landing a loaded RV-4 (Steve Schlieper)
3. 06:34 AM - > Re: Landing a loaded RV-4 (Oldsfolks@aol.com)
Message 1
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| Subject: | Re: Landing a loaded RV-4 |
Jim,
In simple tems I use a limit of 200lbs total aft of the roll bar in my 160HP
wood prop RV4.Carrying heavier folks I add fuel which helps CG. A Landoll dampener,
changing to an Odessey batter and mounting it on the firewall all helped.
I personally only give rides to cute girls under 115 lbs...your call...
Rob Ray
15,000 gallons burned, RV4
jamesbaldwin@dc.rr.com wrote:
James Baldwin wrote:
> Pat -
> From a theoretical point of view I'll give you one answer: the real
simple version. I don't have my reference book in front of me but what
we're obviously talking about here is called static longitudinal
stability. It has everything to do with what you are experiencing and
is strictly a function of loading and the resultant location of the
center of gravity (CG). As the CG moves rearward it approaches the
location of the lift line of the main wing. The tail, for positive
static stability, acts downward and (I am ignoring some cases where
unusual moments or other aerodynamic effects alter this case) is the
variable controlled by the force at the control, or in the case of an
RV, the stick. Obviously as we all experience, the forces required by
the horizontal tail vary with airspeed, thus the need for trim. As the
CG gets close to the lift line location longitudinally, due to passenger
or baggage loading, the force required downward by the horizontal tail
is less and less. Since the downward force required is becoming smaller
as we load more into the rear seat and baggage area it becomes more
sensitive to small stick movements. At the neutral point the tail does
nothing but you'd better HANG ON!
> That's a real simplistic description of what is going on here. RV4s
with lightweight starters, wood props, no mags, etc already have a
rearward bias to the location of the CG and thankfully the arm for these
weight savings is pretty small. I know of one RV6 in particular that
has the opposite problem since he is using an IO360 angle valve with a
CS prop. He runs out of elevator in the flare! He can't do a full
stall landing.
What's the solution? Well, put a CS prop on it. Put an O360 up there.
Is the battery located way up front? Doing something like this is
pretty radical so the other way to look at it is to actually measure the
location of the CG and compare it to what Van dictates as practical
limits. I'm going to guess that you guys are exceeding the rearward
limit that Van specifies as acceptable for decent handling. I don't
have the weight and balance information in front of me but if I remember
I think the limits were something like 15 to 30% MAC (of the mean
aerodynamic chord). The way you find out where you are REALLY flying is
to get three scales and fully load the airplane in a level attitude just
the way the builder did when he finished building, only do it with a
load the way you actually fly it. You and your pax (or weights) sit in
there and then you do the math after getting the weights from the
scales. Now you know what the problem is if my suspicions are correct:
you are outside the weight and balance limits set by Van for your
aircraft. Van knew enough to put a margin in there for all of us but he
also flew enough stuff to know he had to demand handling characteristics
for the "least common denominator" pilot. If I were you, I'd find out
where my CG REALLY is and quit trying to defeat the physics of flight we
all must deal with. Out of the envelope operation can only lead to
disaster when coupled with other factors such as wind, weather, low
fuel, short runways, engine out, etc. Using a forward trim does not
change the effects of a poor loading scenario. In fact it does not
change the slope of the plot of the longitudinal stability (dcm/cg) line
either, it just makes the controls feel better.
> My guess is you'll discover you are operating your airplane outside
the planned envelope and probably you need something more capable. Go
see John Harmon -- he has this thing called a Rocket. JBB
>
> ps -- a big ps here: I can imagine there maybe might be one or two
cases out there where some error in building might bias the CG or wing
location which would adversely affect the normal passenger load handling
characteristic, but probably not, it's probably plain and simple weight
and balance.
>
> PGLong@aol.com wrote:
>> Help.......I have an RV-4 and am experiencing landing problems with a
rear seater present. I installed a Landoll Harmonic Balancer and
according to weight and balance, should be able to tote a 225 pounder
and stay within CG limits with correct fuel loads. Even with a 120-150
pound person in the rear seat, the elevator controls are so light it's
almost like moving nothing. Not sure if I'm over controlling, but it is
so easy to get a hip hop dance down the runway. Friend said to try and
use a significant amount of down elevator trim to help. Haven't tried
that yet but will next flight. What works for others? Just stick with
wheel landings? Lots of friends that would like a ride, but hate to
threaten them while I learn new techniques.
>>
>> Pat Long
>> PGLong@aol.com
>> N120PL
>> RV4
>> Bay City, Michigan
>> 3CM
---------------------------------
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Message 2
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| Subject: | Re: Landing a loaded RV-4 |
Pat,
What is your empty weight for your RV4? Mine is 995, which is about 80
lbs heavier than the planned target of 905-913. With that in mind and
running my own W&B numbers I never even considered anyone over 150
pounds for the rear pax with full fuel and an empty rea comparment. I
only have about 25 hours in mine, so some insight would be valuable. I
have an 320H2D up front with fixed pitch prop, so I am pretty much
standard with a standard VFR panel.
Steve
D. Steven Schlieper
8 Homeplace
Topsham, Maine 04086
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One died for your soul, the other for your freedom."
----- Original Message -----
From: Derrick Aubuchon
To: rv4-list@matronics.com
Sent: Friday, July 06, 2007 12:09 AM
Subject: Re: RV4-List: Landing a loaded RV-4
Hi Pat,
I have about 500 hours on my 4, and this is what I have picked up over
the years,,
225lbs,, for MY airplane, is pretty much at the maximum I would have
in the rear seat.
My basic, "no-brainer" limit is 200lbs. Anything over that, then I
have to start some serious figuring. That 200lb self-imposed limit
assumes my usual load of stuff in the baggage area,, small tool kit,
canopy cover, quart of oil,, etc. Above 200lbs,,, everything in the
baggage area comes out.
Next is fuel.
As the fuel burns the aircraft cg slips aft, which exacerbates the
situation. So I will always start with full tanks and keep the legs
short with a heavy load in the back
As mentioned in your post, the forward trim trick is very important.
It gives the stick somewhat of a "preload," for lack of a better term
and negates most of the effects of hardware slop in the control system.
As an added bonus, after time,,, you will be able to get a feel for the
effectiveness of the trim, and adjust the airspeed over the fence
accordingly.
Just my two cents,,
Derrick Aubuchon
RV-4: N184DA
Jackson/Westover -Amador County (O70)
daubuchon@volcano.net
On Jul 5, 2007, at 11:25 AM, PGLong@aol.com wrote:
Help.......I have an RV-4 and am experiencing landing problems with
a rear seater present. I installed a Landoll Harmonic Balancer and
according to weight and balance, should be able to tote a 225 pounder
and stay within CG limits with correct fuel loads. Even with a 120-150
pound person in the rear seat, the elevator controls are so light it's
almost like moving nothing. Not sure if I'm over controlling, but it is
so easy to get a hip hop dance down the runway. Friend said to try and
use a significant amount of down elevator trim to help. Haven't tried
that yet but will next flight. What works for others? Just stick with
wheel landings? Lots of friends that would like a ride, but hate to
threaten them while I learn new techniques.
Pat Long
PGLong@aol.com
N120PL
RV4
Bay City, Michigan
3CM
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Message 3
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| Subject: | Re: > Re: Landing a loaded RV-4 |
I have landed our first RV-4 with a 240 pound pass. and had to use
FORWARD pressure on the stick on short final to keep the tail up !! I haven't
done THT again but the RV-4 has a lot of control authority.
You are talking mostly about flying techniques. The trim should be used to
set your airspeed for the pattern when you are downwind and slowed to the
proper speed ( I like 60 MPH) then I like to carry about 1000 RPM to control
descent rate ( More if needed).
If you don't slow down to a full stall landing , you will bounce and go
flying some more. Wheel landings are for those who can't fly a proper approach
and can result in a broken prop ,or worse, if you get ham-handed.
Bob Olds
700 hrs in our first RV-4 and 63 in the second ( From our 1100 foot grass
strip ).
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