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psm(at)att.net
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 Posted: Fri Jul 15, 2011 4:24 pm Post subject: Second test flight - N773PM. |
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The weather finally decided to cooperate today for my second flight.
Well, almost cooperate. The scattered clouds at 2000 were more like
broken, so I limited my activities to straight and level flight and a
few simple turns. I am starting to get the feel of the Zodiac XL, but
it seems to be a painfully slow process. I would really have gained a
lot with a 3 or 4 hour checkout, but there was no way I could get that.
I adjusted the rudder cables to deal with the need to stand on the left
rudder on the first flight. That worked! There is still room to kick
the rudder pedals around and get a slightly different position on the
nose wheel and related V-Block, but with the wings level I got the ball
centered without any help from the pedals.
I don't seem to have the heavy left wing many people talk about. I do
have aileron trim and to get the wings level I had a slight right-roll
setting. I also canted the engine to the right as suggested in
Bingelis' book "Firewall Forward". This is mostly done with large
washers in place on the rubber engine mounts.
My first attempt to get the tachometer reading on my Dynon EMS-120
failed. I managed to get it right in flight by changing the second
tachometer count field to 6. There are two fields (left and right?) and
I needed to change both from 4 to 6 to get a reasonable reading on the tach.
I kept a good eye on the cylinder head temperatures and reduced power
whenever I saw over 350 in level flight. I didn't pay much attention to
it while using full power on takeoff. Keeping the CHT green meant
keeping the RPM around 2700 max. This yielded a level cruise indicated
speed of around 110 knots. I hope to be able to run at higher RPM as
the engine gets a little more broken in. I am also scheming various
ways of improving the cooling to achieve a faster cruise speed. The
engine has done nothing but purr like a kitten.
My meager attempt at slow flight got me around 70 KIAS at 2000 RPM -
give or take. I still don't have control of the plane down pat enough
to really hold a desired speed or pitch in slightly bumpy air.
I tried takeoff runs with 1/2 flaps and no flaps. In both cases I
extended the run until the plane really wanted to lift off with just a
slight amount of back pressure on the stick. This gave me nice takeoffs
without the nose jumping up, but it also used up lots of runway. I
would guess the longer run with no flaps was around 1200 feet.
Climb (Vx) from takeoff with 1/2 flaps was much better than no flaps. I
probably didn't do it at the right speed so I won't make any issue over
the actual numbers yet. I also haven't tried taking off with full flaps
yet. Maybe next time.
In general the flight went pretty well. However, I think I have figured
out one thing -- when I grow up I don't think I want to be a test pilot
for a living . . .
Paul
Camas, WA
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dsleepy47
Joined: 15 Dec 2007
Posts: 41
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| Posted: Fri Jul 15, 2011 6:25 pm Post subject: Second test flight - N773PM. |
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Anyone interested in the Vx part of this thread mght want to look here: http://www.experimentalaircraft.info/flight-planning/aircraft-climb-performance.php for some further discussion. Also look here: http://forums.aopa.org/showthread.php?t=74645&highlight=soft+field&page=2 I think if you do the calculations you would find that unless your 601 is very oddly built climb rate will be greatest with a clean wing. One thing I find is that pilots used to high wing planes will almost never pitch up to a high enough AOA to achieve Vx at first in a bubble canopy low wing aircraft because of the difference in the perceived AOA. Even when I brief Cessna pilots what I am going to do When I establish a Vx climb takeoff in my Grumman I can see them stiffen up in the right seat until I point out that the airspeed is stable at 77 Knots because in a Vx climb you can't see anything but sky, cowling and wings plus you are quite reclined in the seat.
Don't confuse ground roll distance with total distance to 50 ft.
I DO NOT recommend doing high AOA takeoffs until you have gotten very comfortable with your aircraft in slow flight at altitude. Be safe out there.
Deems
| Quote: | I tried takeoff runs with 1/2 flaps and no flaps. In both cases I
extended the run until the plane really wanted to lift off with just a
slight amount of back pressure on the stick. This gave me nice takeoffs
without the nose jumping up, but it also used up lots of runway. I
would guess the longer run with no flaps was around 1200 feet.
Climb (Vx) from takeoff with 1/2 flaps was much better than no flaps. I
probably didn't do it at the right speed so I won't make any issue over
the actual numbers yet. I also haven't tried taking off with full flaps
yet. Maybe next time.
|
[quote][b]
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dsleepy47
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psm(at)att.net
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| Posted: Fri Jul 15, 2011 7:56 pm Post subject: Second test flight - N773PM. |
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Hi Deems,
Thanks for the comments and links. I read the first referenced document, and found it interesting but lacking in details. It also seemed to be rather biased. I suspect the universe considered by the author included only part 23 planes that all have somewhat similar (poor) performance. The comment that some manufacturers recommend use of flaps for short field takeoffs is misleading. Indeed some plane manufacturers recommend flaps for all takeoffs. I have flown several such planes including the Cessna 182 and Tecnam Echo Super.
I am convinced that all planes fly faster and with less drag then they can go while rolling on the ground. While it is true flaps introduce some drag they also increase lift. The drag impact is exponential with speed. Put differently, flaps always increase lift and as speed increases they increase drag with much more impact at higher speeds. This suggests at least the possibility that best performance is achieved using flaps for takeoff. Indeed, some planes like the C-182 can barely get in the air at all without flaps.
I didn't see any discussion of the best way to clear obstacles.
I suspect the ideal takeoff method in many planes is to use a small amount of flaps to get off the ground quickly and then to remove those flaps when clear of obstacles. I know the government folks like to talk about 50 foot obstacles, but around here the trees are A LOT taller than 50 feet.
I think the key to understanding the best way to take off is to find the balance between power, airspeed, and flaps. In a plane like mine (Zodiac XL with Jabiru 3300A) there is so much excess power that climb performance should be good at low speeds with any flap setting.
Paul
Camas, WA
On 7/15/2011 7:22 PM, Deems Herring wrote: [quote] Anyone interested in the Vx part of this thread mght want to look here: http://www.experimentalaircraft.info/flight-planning/aircraft-climb-performance.php for some further discussion. Also look here: http://forums.aopa.org/showthread.php?t=74645&highlight=soft+field&page=2 I think if you do the calculations you would find that unless your 601 is very oddly built climb rate will be greatest with a clean wing. One thing I find is that pilots used to high wing planes will almost never pitch up to a high enough AOA to achieve Vx at first in a bubble canopy low wing aircraft because of the difference in the perceived AOA. Even when I brief Cessna pilots what I am going to do When I establish a Vx climb takeoff in my Grumman I can see them stiffen up in the right seat until I point out that the airspeed is stable at 77 Knots because in a Vx climb you can't see anything but sky, cowling and wings plus you are quite reclined in the seat.
Don't confuse ground roll distance with total distance to 50 ft.
I DO NOT recommend doing high AOA takeoffs until you have gotten very comfortable with your aircraft in slow flight at altitude. Be safe out there.
Deems
> I tried takeoff runs with 1/2 flaps and no flaps. In both cases I
> extended the run until the plane really wanted to lift off with just a
> slight amount of back pressure on the stick. This gave me nice takeoffs
> without the nose jumping up, but it also used up lots of runway. I
> would guess the longer run with no flaps was around 1200 feet.
>
> Climb (Vx) from takeoff with 1/2 flaps was much better than no flaps. I
> probably didn't do it at the right speed so I won't make any issue over
> the actual numbers yet. I also haven't tried taking off with full flaps
> yet. Maybe next time.
>
[b]
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