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nybiker13@gmail.com
Guest
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 Posted: Sun Apr 29, 2007 1:47 am Post subject: Weight and descend speed |
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Hi,
Last weekend I flew the heaviest airplane I ever flew, I had two not
so light passengers and my Cessna 172 took a long time to climb to my
desired altitude. Every thing was going as planned but when I was
landing I did not think too much about the weight factor and as soon
as I was on final I noticed my speed decreasing considerably after I
put the last notch of flap down and I had to use more than the normal
power I use to keep the speed up . The landing was smooth but after
landing when thinking about the decreased speed I am a bit unsure
about the cause. So here are my questions:
1. Is weight a factor in slowing the plane down while descending? -
it could be that I might have brought the nose up without noticing ,
but I want to be conclusive about how the weight would effect my
speed while descending.
2. Did I do the right thing by using full flaps and then use power to
keep the speed up or a better strategy would have been to use one
degree lesser flap than I normally do and maintain my required speed?
Any feedback is appreciated, and here is a non-technical question, one
of the awkward things for me in my pre-flight is to ask passengers
about their weight, so does anyone have any tips on how to ask for
the weight of my passengers, without feeling awkward and making them
uncomfortable? Usually I assume the weight of my passengers and do
the weight and balance and then add another ten pounds to the numbers
I assumed and do the weight and balance again to see if we are ok, but
after my last experience I want to stop assuming things and get the
real numbers : )
Thanks,
-Raj |
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ArtP
Guest
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| Posted: Sun Apr 29, 2007 3:30 am Post subject: Re: Weight and descend speed |
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On 28 Apr 2007 13:47:23 -0700, "nybiker13 (AT) gmail (DOT) com"
<nybiker13 (AT) gmail (DOT) com> wrote:
Weight requires lift. Lift causes drag. Drag requires power. More
weight requires more lift, causes more drag, and requires more power. |
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VH-UNR
Guest
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| Posted: Sun Apr 29, 2007 6:12 am Post subject: Re: Weight and descend speed |
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Did you use 40 degree of flap? what i've found from flying C172's and
Station Air with more weight than normal is to use only 30 degrees of
flap. Hell, in a case like yours i'd go flap less. We do that in the
Station Airs with a full load 9 times out of 10. |
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Andrew Sarangan
Guest
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| Posted: Sun Apr 29, 2007 6:12 am Post subject: Re: Weight and descend speed |
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On Apr 28, 4:47 pm, "nybike...@gmail.com" <nybike...@gmail.com> wrote:
| Quote: | Hi,
Last weekend I flew the heaviest airplane I ever flew, I had two not
so light passengers and my Cessna 172 took a long time to climb to my
desired altitude. Every thing was going as planned but when I was
landing I did not think too much about the weight factor and as soon
as I was on final I noticed my speed decreasing considerably after I
put the last notch of flap down and I had to use more than the normal
power I use to keep the speed up . The landing was smooth but after
landing when thinking about the decreased speed I am a bit unsure
about the cause. So here are my questions:
1. Is weight a factor in slowing the plane down while descending? -
it could be that I might have brought the nose up without noticing ,
but I want to be conclusive about how the weight would effect my
speed while descending.
2. Did I do the right thing by using full flaps and then use power to
keep the speed up or a better strategy would have been to use one
degree lesser flap than I normally do and maintain my required speed?
Any feedback is appreciated, and here is a non-technical question, one
of the awkward things for me in my pre-flight is to ask passengers
about their weight, so does anyone have any tips on how to ask for
the weight of my passengers, without feeling awkward and making them
uncomfortable? Usually I assume the weight of my passengers and do
the weight and balance and then add another ten pounds to the numbers
I assumed and do the weight and balance again to see if we are ok, but
after my last experience I want to stop assuming things and get the
real numbers : )
Thanks,
-Raj
|
When the airplane is flown at the same angle of attack, the airspeed
will be higher when heavier, not lower. However, if it is flown at the
same vertical speed, the airspeed will be lower when heavier. The
center of gravity also plays a role. For the same AOA and weight,
moving the CG aft will increase the airspeed due to the reduced wing
loading. Moving it forward will decrease airspeed. So it is difficult
to draw any conclusions without further information on how the
airplane was flown.
As for passenger weight, it is reasonable to use the FAA standard
weight. They are defined for male and female, and for summer and
winter. Add or subtract as necessary for people who appear to be too
large or too small. I would not worry about computing W&B to the last
pound. Some would say it is illegal and/or the airplane is going to
fall out of the sky if you exceed the published limits even by a small
amount. I would bet that any person who flies an airplane at the
allowed maximum gross weight is actually flying it illegally. The
published W&B for the airplane is likely to be many years old.
Airplanes do gain weight over time, and even a person's weight varies
considerably during the day. If you had a full meal, you could be a
couple of pounds heavier. If you are constipated, you will be heavier.
The only way to do this correctly every singe time is to weigh each
passenger before boarding and also weight the airplane. Obviously no
one does it this way. Even the FAA is not going to ask you to step on
a scale during a ramp check. |
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d&tm
Guest
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| Posted: Sun Apr 29, 2007 6:12 am Post subject: Re: Weight and descend speed |
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<nybiker13 (AT) gmail (DOT) com> wrote in message
news:1177793243.501352.55320 (AT) l77g2000hsb (DOT) googlegroups.com...
| Quote: | Hi,
Last weekend I flew the heaviest airplane I ever flew, I had two not
so light passengers and my Cessna 172 took a long time to climb to my
desired altitude. Every thing was going as planned but when I was
landing I did not think too much about the weight factor and as soon
as I was on final I noticed my speed decreasing considerably after I
put the last notch of flap down and I had to use more than the normal
power I use to keep the speed up . The landing was smooth but after
landing when thinking about the decreased speed I am a bit unsure
about the cause. So here are my questions:
1. Is weight a factor in slowing the plane down while descending? -
it could be that I might have brought the nose up without noticing ,
but I want to be conclusive about how the weight would effect my
speed while descending.
2. Did I do the right thing by using full flaps and then use power to
keep the speed up or a better strategy would have been to use one
degree lesser flap than I normally do and maintain my required speed?
Any feedback is appreciated, and here is a non-technical question, one
of the awkward things for me in my pre-flight is to ask passengers
about their weight, so does anyone have any tips on how to ask for
the weight of my passengers, without feeling awkward and making them
uncomfortable? Usually I assume the weight of my passengers and do
the weight and balance and then add another ten pounds to the numbers
I assumed and do the weight and balance again to see if we are ok, but
after my last experience I want to stop assuming things and get the
real numbers : )
Attitude for Speed |
Power for Altitude.
you would have a greater rate of descent at a higher weight and perhaps you
were subconsiously raising the nose to compensate. If your attitude is
right your speed will be right, and then you adjust rate of descent with
power. If struggling to make the field or to clear obstacles then less flap
can be used.
If I thought I was anywhere near max wt I would not just ask my pax , I
would use the scales at the airport and be sure. I am sure the pax would
would understand and appreciate your professionalism in doing so.
terry |
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Margy Natalie
Guest
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| Posted: Sun Apr 29, 2007 6:12 am Post subject: Re: Weight and descend speed |
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nybiker13 (AT) gmail (DOT) com wrote:
| Quote: | Hi,
Any feedback is appreciated, and here is a non-technical question, one
of the awkward things for me in my pre-flight is to ask passengers
about their weight, so does anyone have any tips on how to ask for
the weight of my passengers, without feeling awkward and making them
uncomfortable? Usually I assume the weight of my passengers and do
the weight and balance and then add another ten pounds to the numbers
I assumed and do the weight and balance again to see if we are ok, but
after my last experience I want to stop assuming things and get the
real numbers : )
Thanks,
-Raj
|
If taking a couple flying I always ask "how much do you and your husband
weigh together"? I have also been know to say "I have 250 lbs, will
that work?". When it looks real close I just ask. You get used to it
after a while.
Margy |
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Crash Lander
Guest
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| Posted: Mon Apr 30, 2007 6:13 am Post subject: Re: Weight and descend speed |
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<nybiker13 (AT) gmail (DOT) com> wrote in message
news:1177793243.501352.55320 (AT) l77g2000hsb (DOT) googlegroups.com...
| Quote: | .....I had to use more than the normal
power I use to keep the speed up .
|
Attitude controls speed.
Throttle controls altitude.
Oz Lander |
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nybiker13@gmail.com
Guest
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| Posted: Mon Apr 30, 2007 6:13 am Post subject: Re: Weight and descend speed |
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Thanks a bunch for all your feeback, and I will keep that in mind on
my next flight and try to figure out the exact reason - and to answer
VH-UNR's question: I used 40 degrees of flap.
Thanks again,
-Raj |
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Brian
Guest
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| Posted: Mon Apr 30, 2007 9:45 pm Post subject: Re: Weight and descend speed |
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The CG shift would most likely cause the aircraft to want to slow on
Final.
Having the CG aft will lighten the control forces so if you are used
to holding some back pressure on final, it will be less with a more
aft CG. Also the Trim will probably be positioned in a different spot
than with a more forward CG.
I once inadvertantly loaded a C-172 behind the aft CG limit, I
actually had to hold forward pressure on the yoke to maintain the
proper attitude during the flare.
I would not have added any more flap once I determined I was low or
slow. For normal landings I think adding more than 10 degrees of flap
and then adding power to compensate for it is kind of like stepping on
the brake and the gas pedal at the same time in your car.
Brian
CFIIG/ASEL |
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Morgans
Guest
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| Posted: Wed May 02, 2007 6:13 am Post subject: Re: Weight and descend speed |
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"kevmor" <kevmor (AT) gmail (DOT) com> wrote in message
news:1178069817.885752.182540 (AT) o5g2000hsb (DOT) googlegroups.com...
| Quote: | Having the CG aft would require more control deflection though, since
there is a shorter arm from the CG to the elevator, correct?
|
Only the distance of the arm is not the important factor, in this case.
With the CG to the most rear point, the CG is at virtually the same location
as the center of lift. Think of the airplane as though it is balanced on a
pin. It only takes a very small push to send it tilting one way or the
other.
With a forward CG, the plane will go into a dive very easily; more easily
than with the CG aft. It takes a whole lot of movement to get it to climb,
though. That is why on most plans, the elevator throw is something like
3/4" up, and 1/2" down.
--
Jim in NC |
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kevmor
Guest
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| Posted: Wed May 02, 2007 6:13 am Post subject: Re: Weight and descend speed |
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Having the CG aft would require more control deflection though, since
there is a shorter arm from the CG to the elevator, correct?
On Apr 30, 9:45 am, Brian <brianfc...@msn.com> wrote:
| Quote: | Having the CG aft will lighten the control forces so if you are used
to holding some back pressure on final, it will be less with a more
aft CG. Also the Trim will probably be positioned in a different spot
than with a more forward CG. |
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Roger (K8RI)
Guest
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| Posted: Thu May 03, 2007 9:59 pm Post subject: Re: Weight and descend speed |
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On Tue, 1 May 2007 22:20:48 -0400, "Morgans"
<jsmorgan (AT) charterJUNK (DOT) net> wrote:
| Quote: |
"kevmor" <kevmor (AT) gmail (DOT) com> wrote in message
news:1178069817.885752.182540 (AT) o5g2000hsb (DOT) googlegroups.com...
Having the CG aft would require more control deflection though, since
there is a shorter arm from the CG to the elevator, correct?
Only the distance of the arm is not the important factor, in this case.
With the CG to the most rear point, the CG is at virtually the same location
as the center of lift. Think of the airplane as though it is balanced on a
pin. It only takes a very small push to send it tilting one way or the
other.
With a forward CG, the plane will go into a dive very easily; more easily
than with the CG aft. It takes a whole lot of movement to get it to climb,
though. That is why on most plans, the elevator throw is something like
3/4" up, and 1/2" down.
|
I once had a passenger in the Cherokee 180 who li...er wasn't very
accurate on his weight. Actually the number he gave me was FAR more
than optimistic and must have been what he was wishing he weighed.
At any rate the flight had well and we were lined up on final coming
to set down on the touch down zone. I pulled the power over the
numbers and the nose dropped (not a stall). I firewalled it and
arrested the sink rate just in time, but we richoceted off the runway.
Working with the throttle I managed to reduce the oscilation and made
a good landing AFTER the spectacular part that happened to be right in
front of a 210 waiting at the hold line. |
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Morgans
Guest
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| Posted: Fri May 04, 2007 2:31 am Post subject: Re: Weight and descend speed |
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"Morgans" > wrote
| Quote: | That is why on most plans, the elevator throw is something like 3/4" up,
and 1/2" down.
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Crap. Even though what I posted about CG's is conceptually correct, the bit
about 3/4" and 1/2" control throws was intended for (where I thought I was)
the model airplane group. Sorry! <g>
--
Jim in NC |
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Dudley Henriques
Guest
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| Posted: Sat May 05, 2007 9:14 pm Post subject: Re: Weight and descend speed |
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"Roger (K8RI)" <validaddress (AT) my (DOT) com> wrote in message
news:dq4k33tvbat0rrstdlvloa2mp97ivgac6i (AT) 4ax (DOT) com...
| Quote: | Working with the throttle I managed to reduce the oscilation and made
a good landing AFTER the spectacular part that happened to be right in
front of a 210 waiting at the hold line.
|
This is ok unless the people in the 210 got out of the airplane and held up
2 foot by 3 foot cards each with numbers showing below 5.0
Dudley |
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