Short field takeoff climb speed?
Many many planes are flown overloaded and there is another big factor to take into account. Every 1% extra weight is about 2-3% extra runway needed.
Plus a higher Vr value.
Plus a higher Vr value.
Finally, worth realising that (except in extreme obstacle clearance scenarios rarely present in Europe) the feet/minute climb rate is not very dependent on the climb speed.
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44/50 sounds dangerous to me. Im a student at Netherthorpe in 130hp C-150A's so please dont take my word as gospel, but instructors teach to pull the nosewheel off at 45kts and start to bring the rear undercarriage off the ground at 50kts.
Immediately after takeoff, nose level (or almost level) and accellerate to 55kts and slowly pitch back a 60-65kt climb.
I remember once an instructor took control after a touch and go; in takeoff configuration the stall warner was sounding when attempting a 50kt climb... Lets just say i was a tad scared that the port wing was suddenly going to take a liking to the ground!
Immediately after takeoff, nose level (or almost level) and accellerate to 55kts and slowly pitch back a 60-65kt climb.
I remember once an instructor took control after a touch and go; in takeoff configuration the stall warner was sounding when attempting a 50kt climb... Lets just say i was a tad scared that the port wing was suddenly going to take a liking to the ground!
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I had a restless night last Sunday lying in bed worrying about departure from Lausanne in my Mooney.
Three 200lb + males plus bags plus fuel, OAT +26C, 2000ft amsl with an 850m runway with a significant bowl shape to it - 2.5% downslope initially and a 5kt headwind component.
I was regretting having left the POH in the aircraft but the hotel had free internet downstairs so I crept down in the middle of the night and downloaded what performance charts I could from the web, these allayed most of my fears.
Before we took off I also went through the POH performance charts which confirmed we would be OK for the prevailing conditions and added 120L of avgas which kept us well within the comfort zone both for takeoff and cruise back to the UK + diversion (our destination was 200m vis in FG when we departed Lausanne with an optimistic TAF to clear by our arrival time - which it duly did) .
As it happened we were fine, I ran the engine up to max power on the displaced threshold while just holding it with the brakes, released the brakes and used only 70% of the available runway, taking off on rwy18 helped with the acceleration being brisk and we lifted off with the stall warner bleating at 65kt into ground effect whilst still on the downhill segment of the bowl.
Lower the nose a tad, stall warner goes, touch of brakes, wheels up, more lift, less drag, leave 10 deg flaps down to help the initial climb and we were on our way.
The POH is pretty accurate, there are performance charts for just about every phase of flight and I find it reassuring to use them when hot, high and heavy.
SB
Three 200lb + males plus bags plus fuel, OAT +26C, 2000ft amsl with an 850m runway with a significant bowl shape to it - 2.5% downslope initially and a 5kt headwind component.
I was regretting having left the POH in the aircraft but the hotel had free internet downstairs so I crept down in the middle of the night and downloaded what performance charts I could from the web, these allayed most of my fears.
Before we took off I also went through the POH performance charts which confirmed we would be OK for the prevailing conditions and added 120L of avgas which kept us well within the comfort zone both for takeoff and cruise back to the UK + diversion (our destination was 200m vis in FG when we departed Lausanne with an optimistic TAF to clear by our arrival time - which it duly did) .
As it happened we were fine, I ran the engine up to max power on the displaced threshold while just holding it with the brakes, released the brakes and used only 70% of the available runway, taking off on rwy18 helped with the acceleration being brisk and we lifted off with the stall warner bleating at 65kt into ground effect whilst still on the downhill segment of the bowl.
Lower the nose a tad, stall warner goes, touch of brakes, wheels up, more lift, less drag, leave 10 deg flaps down to help the initial climb and we were on our way.
The POH is pretty accurate, there are performance charts for just about every phase of flight and I find it reassuring to use them when hot, high and heavy.
SB
I flew some Forest Service officials to an airport with a relatively short field length, in a Shrike Twin Commander. We were part of a large fire in Southern California, and they wanted this field because it was near the main fire camp, where they had a meeting. As they were waiting for their ride, I quickly reviewed the performance, looked at the temperatures for the day, and told them we'd have to leave by 11:00, or couldn't leave until evening. That cut short their meeting time. They weren't happy.
They tried bargaining. They wanted to see the numbers. They tried demanding. Said they'd report me to my employer; pressure was applied. I held firm. The numbers said we could go; we could get off the ground in the required distance...but I also noted powerlines all around the field. It just became a lot shorter. Yes, on paper, it looked okay. But what if we lost power, or an engine, on takeoff. What if the gear didn't retract? What if we had any number of problems that meant we couldn't meet that criteria? If we were just on the edge of making it out, then it left insufficient margin for something to go wrong...and we never plan for things to go right.
Everything should be planned with the worse case scenario in mind. Not what could go wrong, but what will go wrong. Not what if, but instead, when.
I offered them choices. I gave them departure deadlines based on the temperature increase for the day. I offered to reposition the airplane to a different airport, farther away, to pick them up. Or leave some behind. Or I could depart and burn fuel, and return. At length they agreed. My sole concern was their safety and the safety of flight, with all else being far in second place. So it needs to be with every takeoff.
As others have rightly said several times now...being conservative is a good thing. If you're going to depend on the book distances, then you're going to have to fly the book airspeeds to make it work. When you do calculate it, though, do it for the worse case scenario.
Something we often do to build in a margin of safety is use "assumed temperatures." This isn't assumed as in guessed, but assumed as in planning the takeoff based on a theoretical higher temperature (and therefore, density altitude). If the airplane could make the takeoff safely at the greater temperature, then we know it could certainly do so at the present temperature. If it's 15 degrees at the time of takeoff, but we determine it can be safely done at 30 degrees outside air temp, then we've got a safety performance factor built in. We'll sometimes use this to apply a power reduction factor to still safely make the takeoff, something that's not necessary or done in light piston airplanes...but the point is that being conservative and allowing more distance and allowing for reduced performance is a prudent and even a professional thing to do. It's standard procedure in most professional cockpits; acting conservatively should be standard procedure in any cockpit.
Good job pulling the performance charts and using them, Scooter Boy. That's exactly why the charts are there. Your example is one everyone can take heed, and follow.
They tried bargaining. They wanted to see the numbers. They tried demanding. Said they'd report me to my employer; pressure was applied. I held firm. The numbers said we could go; we could get off the ground in the required distance...but I also noted powerlines all around the field. It just became a lot shorter. Yes, on paper, it looked okay. But what if we lost power, or an engine, on takeoff. What if the gear didn't retract? What if we had any number of problems that meant we couldn't meet that criteria? If we were just on the edge of making it out, then it left insufficient margin for something to go wrong...and we never plan for things to go right.
Everything should be planned with the worse case scenario in mind. Not what could go wrong, but what will go wrong. Not what if, but instead, when.
I offered them choices. I gave them departure deadlines based on the temperature increase for the day. I offered to reposition the airplane to a different airport, farther away, to pick them up. Or leave some behind. Or I could depart and burn fuel, and return. At length they agreed. My sole concern was their safety and the safety of flight, with all else being far in second place. So it needs to be with every takeoff.
As others have rightly said several times now...being conservative is a good thing. If you're going to depend on the book distances, then you're going to have to fly the book airspeeds to make it work. When you do calculate it, though, do it for the worse case scenario.
Something we often do to build in a margin of safety is use "assumed temperatures." This isn't assumed as in guessed, but assumed as in planning the takeoff based on a theoretical higher temperature (and therefore, density altitude). If the airplane could make the takeoff safely at the greater temperature, then we know it could certainly do so at the present temperature. If it's 15 degrees at the time of takeoff, but we determine it can be safely done at 30 degrees outside air temp, then we've got a safety performance factor built in. We'll sometimes use this to apply a power reduction factor to still safely make the takeoff, something that's not necessary or done in light piston airplanes...but the point is that being conservative and allowing more distance and allowing for reduced performance is a prudent and even a professional thing to do. It's standard procedure in most professional cockpits; acting conservatively should be standard procedure in any cockpit.
Good job pulling the performance charts and using them, Scooter Boy. That's exactly why the charts are there. Your example is one everyone can take heed, and follow.
Scooter Boy, "...leave 10 deg flaps down to help the initial climb..."? Unless my understanding of aerodynamics & performance is wrong, leaving any flap down will adversely affect climb performance although the shorter take-off run compensates for some of this loss by allowing the climb to commence earlier. Even so, at some point there will be a crossover point where leaving flap down results in reduced net climb performance.
That depends on the airplane. Some airplanes experience better performance with a little flap, some with none, and some with a reflexed flap.
I've flown airplanes that not only benefited from flap for takeoff, but also for climb...several, in fact.
I've flown airplanes that not only benefited from flap for takeoff, but also for climb...several, in fact.
I think SNS3Guppy's explanation is clear and sensible. You should never accept given performance figures without properly considering whether your environmental and runway figures match those used to create the performance table. And remember too, that those figures were calculated by a test pilot in a new aircraft with new engine and propellor and probably without the usual aviation related junk lurking behind the seats! I doubt you'll quite match those performance figures even on a good day, hence the need for a safety factor!
But in any case I can't think of any airfield in England where you would perform a short field take off in order to get off the ground in the shortest possible ground roll, then have no option but to climb at Vx until over a hill, mountain, power line or anything else at any significant distance from the departure end of the runway. In reality, if faced with such a restrictive and dangerous airfield, I wouldn't go there and neither would anyone else!
Isn't the reality that we use a shortfield take off to get off the ground in the shortest distance, climb to 50 ft at Vx, level off in order to collect a few knots of airspeed, before climbing at Vy?
But in any case I can't think of any airfield in England where you would perform a short field take off in order to get off the ground in the shortest possible ground roll, then have no option but to climb at Vx until over a hill, mountain, power line or anything else at any significant distance from the departure end of the runway. In reality, if faced with such a restrictive and dangerous airfield, I wouldn't go there and neither would anyone else!
Isn't the reality that we use a shortfield take off to get off the ground in the shortest distance, climb to 50 ft at Vx, level off in order to collect a few knots of airspeed, before climbing at Vy?
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Tinstaafl,
It is counter-intuitive but 10 deg flap helps the initial segment of a steep climb in my aircraft.
All to do with angle of attack and relative wind.
There is a clear explanation of the reasons for this in "piloting for maximum performance" by Lewis Bjork.
Amazon.com have it for $6 - it really is a great read, well written, relevant and full of get-you-out-of-trouble wisdom.
SB
It is counter-intuitive but 10 deg flap helps the initial segment of a steep climb in my aircraft.
All to do with angle of attack and relative wind.
There is a clear explanation of the reasons for this in "piloting for maximum performance" by Lewis Bjork.
Amazon.com have it for $6 - it really is a great read, well written, relevant and full of get-you-out-of-trouble wisdom.
SB
