Porpoising on take-off?!
Join Date: May 2006
Location: Down South, preferably inverted
Posts: 235
Received 0 Likes
on
0 Posts
Quote:
Just waiting for the licence
Congrats
. That 3 week wait is agonising. Only decision now is to either be "captain sensible" and build confidence or whether you take everyone you know flying straight away. I opted for the latter.
Just waiting for the licence
Congrats
. That 3 week wait is agonising. Only decision now is to either be "captain sensible" and build confidence or whether you take everyone you know flying straight away. I opted for the latter.
.......... Just because you can........ now.....
Try 'rotating' something like a Chipmunk....
In any case, you do not 'pull back on the control column', you use the control column to select the correct attitude for the initial climb. In some light aircraft that's only fractionally different to the runway attitude during the take off roll.
In any case, you do not 'pull back on the control column', you use the control column to select the correct attitude for the initial climb. In some light aircraft that's only fractionally different to the runway attitude during the take off roll.
Last edited by BEagle; 12th Aug 2008 at 10:20.
Thread Starter
Join Date: Jan 2006
Location: Chester
Posts: 142
Likes: 0
Received 0 Likes
on
0 Posts
Frontlefthamster - don't 'diss' my original question. The replies have been very helpful actually, with real accounts of the situation happening. Wind your neck in! 
Join Date: Sep 2005
Location: Norfolk UK
Age: 81
Posts: 1,200
Likes: 0
Received 0 Likes
on
0 Posts
T/O
BEagle is spot on.
In simple terms,the aircraft takes off when it wants to if you have the stick /column just very,very slightly back,almost imperceptible pressure exerted.
Well it does in the L4 with all of it's 65 hp,and did so like this yesterday.
Another fault,anyway it was with me to start with,is to keep the aircraft forced onto the runway because you think the speed is too low,when it actually wants to fly away.
Lastly, there is a tremondous amount of knowledge on this forum,you just have to filter out the odd facetious remark.
Lister
In simple terms,the aircraft takes off when it wants to if you have the stick /column just very,very slightly back,almost imperceptible pressure exerted.
Well it does in the L4 with all of it's 65 hp
,and did so like this yesterday.Another fault,anyway it was with me to start with,is to keep the aircraft forced onto the runway because you think the speed is too low,when it actually wants to fly away.
Lastly, there is a tremondous amount of knowledge on this forum,you just have to filter out the odd facetious remark.
Lister
Join Date: Oct 2005
Location: USA
Posts: 3,218
Likes: 0
Received 0 Likes
on
0 Posts
One of the airplanes I fly is the Air Tractor AT-802, which is a single engine conventional gear (tailwheel) airplane. The act of getting it into the air can occur from a three point attitude, or with the tail in the air; the physical change in the pitch attitude is to "rotate" downward, or nose down, to get the tail in the air, in order to accelerate faster and get off the ground.
Even though after that the aircraft flies off in nearly a level attitude, we still generally refer to this as rotation...not when the nose pitches down, and even though the nose doesn't pitch up after that, it's still generally referred to as rotation.
Regardless, so long as everyone knows what you're talking about, lift-off, unstick, takeoff, whatever...works. A lot of light airplanes start begging to go fly as they get light on the gear, skipping and hopping and ready to go, unless they're allowed to come off or coaxed off with a little back stick pressure. Sometimes it's a fine line between a fast taxi, and a takeoff. Sometimes the airplane comes off in a three point tailwheel attitude, sometimes a three point nosewheel attitude, and sometimes a two point attitude, either way.
The terminology really isn't that important. Generally speaking, it's still "rotation," no matter what you have to do to get it there. Call it what floats your boat, so long as you do it before you reach the far end where the little red lights are.
Even though after that the aircraft flies off in nearly a level attitude, we still generally refer to this as rotation...not when the nose pitches down, and even though the nose doesn't pitch up after that, it's still generally referred to as rotation.
Regardless, so long as everyone knows what you're talking about, lift-off, unstick, takeoff, whatever...works. A lot of light airplanes start begging to go fly as they get light on the gear, skipping and hopping and ready to go, unless they're allowed to come off or coaxed off with a little back stick pressure. Sometimes it's a fine line between a fast taxi, and a takeoff. Sometimes the airplane comes off in a three point tailwheel attitude, sometimes a three point nosewheel attitude, and sometimes a two point attitude, either way.
The terminology really isn't that important. Generally speaking, it's still "rotation," no matter what you have to do to get it there. Call it what floats your boat, so long as you do it before you reach the far end where the little red lights are.
Join Date: Oct 2005
Location: USA
Posts: 3,218
Likes: 0
Received 0 Likes
on
0 Posts
Gemma,
Sometimes when one sees a runway that's 12,000 feet long, it seems excessive...especially if one is flying an airplane which requires 1,200 feet. Some large airplanes however, need it (reference the video).
When I flew large air tankers, we used fields more suited to small airplanes, sometimes, because those fields had been selected as central to the areas in which we fought fire. It wasn't uncommon at all to roll full length, or occasionally right off the end as we became airborne. I've stood at the end of the runway at Hemet (California, USA) and watched other tankers rotate, sucking clods of earth out of the ground from wing tip vortices with a very aggressive rotation, followed by the gear clearing the fence at the end by a few feet. I departed Reno-Stead in a C-130, a few years ago where the Reno Air Races are held each year. Reno sits in a bowl, with rising terrain around it....not very high terrain in most cases, but rising terrain. We got off the ground, but couldn't clear the terrain and had to fly the air race course around the pylons as we flew around the valley scratching for altitude. I did the same thing last year in single engine tanker, much of it for the first lap below 15', because due to the temperature and downdrafts from high winds, the airplane just wouldn't climb. I used all the runway.
Presently (airline freight) we depart at 833,000 lbs, and just as the ground school instructor said on day one...we see the red lights on every takeoff. We calculate everything into the takeoff; runway slope, wind, wet runways, weight, climb performance after takeoff, accelerate stop, accelerate go, refusal distance, speed, runway remaining, time to dump fuel to return in an emergency, commit speeds with an engine failure, brake settings, power settings, etc...it all gets figured out for each takeoff. We have an exact speed and pitch attitude to achieve for rotation. An early or late rotation throws all the calculations out the window and increases the distance. No matter how much we might want to rotate as we see those red lights coming up, we can't.
The russian airplane in the video went a bit farther than we might have done. We do have minimum altitudes alluded to earlier in this thread, but they're very small, called a "screen height" that are part of performance calculations. Generally speaking, the takeoff distance is calculated to be the longer of either the balanced field length, or that necessary to achieve a 35 foot screen height (15' in wet weather). Balanced field is when the distance to accelerate to decision speed, lose an engine and take off, and to do the same and stop...when those distances are the same, ...or the distance to take off with engines and achieve a height of 35'...that's our minimum runway. Whichever is longer. The ruskies appear to be working without those margins in the video, which is the same way we worked in tankers.
It's much simpler,and a whole lot more fun, in a light airplane, when one gets to feel the airplane into the air. In a large airplane, it's all numbers, which takes some of the fun out of it.
Sometimes when one sees a runway that's 12,000 feet long, it seems excessive...especially if one is flying an airplane which requires 1,200 feet. Some large airplanes however, need it (reference the video).
When I flew large air tankers, we used fields more suited to small airplanes, sometimes, because those fields had been selected as central to the areas in which we fought fire. It wasn't uncommon at all to roll full length, or occasionally right off the end as we became airborne. I've stood at the end of the runway at Hemet (California, USA) and watched other tankers rotate, sucking clods of earth out of the ground from wing tip vortices with a very aggressive rotation, followed by the gear clearing the fence at the end by a few feet. I departed Reno-Stead in a C-130, a few years ago where the Reno Air Races are held each year. Reno sits in a bowl, with rising terrain around it....not very high terrain in most cases, but rising terrain. We got off the ground, but couldn't clear the terrain and had to fly the air race course around the pylons as we flew around the valley scratching for altitude. I did the same thing last year in single engine tanker, much of it for the first lap below 15', because due to the temperature and downdrafts from high winds, the airplane just wouldn't climb. I used all the runway.
Presently (airline freight) we depart at 833,000 lbs, and just as the ground school instructor said on day one...we see the red lights on every takeoff. We calculate everything into the takeoff; runway slope, wind, wet runways, weight, climb performance after takeoff, accelerate stop, accelerate go, refusal distance, speed, runway remaining, time to dump fuel to return in an emergency, commit speeds with an engine failure, brake settings, power settings, etc...it all gets figured out for each takeoff. We have an exact speed and pitch attitude to achieve for rotation. An early or late rotation throws all the calculations out the window and increases the distance. No matter how much we might want to rotate as we see those red lights coming up, we can't.
The russian airplane in the video went a bit farther than we might have done. We do have minimum altitudes alluded to earlier in this thread, but they're very small, called a "screen height" that are part of performance calculations. Generally speaking, the takeoff distance is calculated to be the longer of either the balanced field length, or that necessary to achieve a 35 foot screen height (15' in wet weather). Balanced field is when the distance to accelerate to decision speed, lose an engine and take off, and to do the same and stop...when those distances are the same, ...or the distance to take off with engines and achieve a height of 35'...that's our minimum runway. Whichever is longer. The ruskies appear to be working without those margins in the video, which is the same way we worked in tankers.
It's much simpler,and a whole lot more fun, in a light airplane, when one gets to feel the airplane into the air. In a large airplane, it's all numbers, which takes some of the fun out of it.
Join Date: Apr 2008
Location: Cilboldentune, Britannia
Posts: 555
Likes: 0
Received 0 Likes
on
0 Posts
A word of caution about 'lifting' off too early - you may not have full aileron control and may not be able to stop a roll. Most POHs quote an 'unstick' speed for a reason.
Lift off too early, and you might be only able to fly while in the ground effect, with too much drag to build up speed without dropping the nose and touching down again - assuming you have enough runway left.
(It isn't easy to do this, but it has lead to accidents)
(It isn't easy to do this, but it has lead to accidents)
Moderator
It is easy to do that on Piper PA28's, I was a passenger to a pilot who did it in an Arrow, The only way we made it out is that I retracted the gear, and the reduced drag let us climb away. It was a risk, but the runway was gone anyway. I later experimented in a PA28-140 on the long frozen lake. even at light weight, it is surprizingly easy to get the nose so high that you could not climb out of ground effect without landing back. I did it many times.
I do not support the dependance on numbers in light aircraft, as much as I expect that pilots should be able to "feel" the plane. If you are watching the instruments, you are not feeling the subtle cues that the aircraft is offering, and you're not learning as much. Hopefully your night training is including zero instrument lighting (for simulated electrical failures) so you have only the feel of the plane to go by. That's where you'll be able to feel when flaps should be selected up or down. If the operator asks to have their procedures followed, then you are bound by respect to do that, but regognize it as a safety procedure, which may be more restrictive than the aircraft manufacturer intended.
Pilot DAR
I do not support the dependance on numbers in light aircraft, as much as I expect that pilots should be able to "feel" the plane. If you are watching the instruments, you are not feeling the subtle cues that the aircraft is offering, and you're not learning as much. Hopefully your night training is including zero instrument lighting (for simulated electrical failures) so you have only the feel of the plane to go by. That's where you'll be able to feel when flaps should be selected up or down. If the operator asks to have their procedures followed, then you are bound by respect to do that, but regognize it as a safety procedure, which may be more restrictive than the aircraft manufacturer intended.
Pilot DAR
