Question about performance charts

[jasc15]

I notice my POH (Piper Warrior) only has performance charts for short field, and obstacle clearance take off, but not normal take off. While doing a flight plan, I obviously need to know what my take off distances will be, so what gives??

 

[MikePapa]

I'm not familiar with the POH in question, but I wouldn't be surprised if they only list short field takeoff distances. If you are concerned about takeoff distances, why would you not be doing a short field takeoff?

 

[jesse]

I notice my POH (Piper Warrior) only has performance charts for short field, and obstacle clearance take off, but not normal take off. While doing a flight plan, I obviously need to know what my take off distances will be, so what gives??

In something like a Warrior -- it is not likely that your takeoff technique will be much different for short-field versus normal field. I mean, you don't have temperatures going through the roof or a second engine that can fail.

I use the same technique in a Cherokee 180. It doesn't matter if it is 1800 feet or 13,000 feet...I do it the same way.

Keep in mind that "short field" doesn't really mean soft field (instructors often shove them together. true soft field makes for a long takeoff)...If it is truly a "soft field" you probably shouldn't be trying it with the nosewheel anyways.

 

[jasc15]

I'm not familiar with the POH in question, but I wouldn't be surprised if they only list short field takeoff distances. If you are concerned about takeoff distances, why would you not be doing a short field takeoff?

So you are saying i shouldn't have to worry about figuring out TO distance unless the field length makes me question my TO performance??

In something like a Warrior -- it is not likely that your takeoff technique will be much different for short-field versus normal field. I mean, you don't have temperatures going through the roof or a second engine that can fail.

Well, for a normal take off i dont hold the breaks while bringing the engine up to full power, so that makes my technique different for normal and short TO.

Keep in mind that "short field" doesn't really mean soft field (instructors often shove them together. true soft field makes for a long takeoff)...If it is truly a "soft field" you probably shouldn't be trying it with the nosewheel anyways.

Yea, that makes sense, but we've made a clear distinction between short and soft TOs

 

[SkyHog]

My old Cherokee only had short field performance numbers too. The reason? If its short, you use short field techniques, otherwise, you'll have enough runway.

It may not be precise, but really, if you have 6000ft of runway, and you're not in the mountains, who cares how you take off? You'll be fine.

 

[jesse]

Well, for a normal take off i dont hold the breaks while bringing the engine up to full power, so that makes my technique different for normal and short TO.

Given the amount of time it takes your engine to develop full power -- bringing the engine up to full power with the brakes fully set does not help your hsort field take-off. In fact, it hurts your takeoff distance and is hard on your prop and brakes.

Don't come to a complete stop and smoothly go to full power. It's way more efficient. I always do a short-field takeoff from a roll that I develop before I'm even aligned with the runway.

 

[MikePapa]

So you are saying i shouldn't have to worry about figuring out TO distance unless the field length makes me question my TO performance??

You should always worry about takeoff distance, it's just that sometimes there's no real need to precisely calculate what it is.

For the 182, at 8000' pressure altitude and 70 degrees, the ground roll is 1720' for a short field take off at max gross. (assuming a paved field, no wind). If I throw in 20% for the wife and kids, that's 2064'. Naturally any obstacles are going to affect my planning also.

So do I really need to put pen to paper if I'm taking off from a 8,000' runway from a sea level airport in January? Not really, and I'm not going to be doing a short field takeoff anyway. However, I should have a general idea how much ground roll I'm go use to get off the ground and I should have an abort point in mind before I ever throw the coals to it. This comes from knowing your airplane and yourself, but that's really also a factor for short field takeoffs also.

That's just my $0.02 worth and BTW, most POH I have seen don't include takeoff distances for normal takeoff procedures, but I certainly haven't seen a great number of them.

 

[MikePapa]

Given the amount of time it takes your engine to develop full power -- bringing the engine up to full power with the brakes fully set does not help your hsort field take-off. In fact, it hurts your takeoff distance and is hard on your prop and brakes.

I'm not saying it's wrong, but I don't really understand your reasoning here. For every short takeoff competition I've seen, it always appears as if the pilots do a static run-up. Also my understanding is that the wear on brakes comes mostly from friction and heat, and there's very little of that in a static run-up.

 

[jesse]

I'm not saying it's wrong, but I don't really understand your reasoning here. For every short takeoff competition I've seen, it always appears as if the pilots do a static run-up. Also my understanding is that the wear on brakes comes mostly from friction and heat, and there's very little of that in a static run-up.

Try it. I have. I suspect they have everyone start from a stop because it's a constant and some folks probably aren't comfortable starting from a roll.

It does not take long to develop full power on a Cherokee. If you're already rolling, why come to a complete stop, then go full power, then start again. It doesn't really help. Some airplanes it might make sense..but it does not in a Cherokee.

 

[gprellwitz]

Try it. I have. I suspect they have everyone start from a stop because it's a constant and some folks probably aren't comfortable starting from a roll.

It does not take long to develop full power on a Cherokee. If you're already rolling, why come to a complete stop, then go full power, then start again. It doesn't really help. Some airplanes it might make sense..but it does not in a Cherokee.

Jesse, are you presuming that you don't need to do a 180 before taking off? Or are you saying that even if you're going slow enough that you can do a 180 (on a grass runway in the situation I have in mind) it's still beneficial to go right into the roll as you line up?

Other benefits of doing the no-stop method are better cooling of the engine and less chance of pulling rocks into the prop.

 

[poadeleted20]

In something like a Warrior -- it is not likely that your takeoff technique will be much different for short-field versus normal field.

IIRC, even ignoring the rolling vs standing start issues, short-field in a PA28 is still very different from normal -- 25 vs zero flaps, and rotation/lift-off at significantly lower speed, which gives you a much shorter takeoff roll.

 

[jesse]

IIRC, even ignoring the rolling vs standing start issues, short-field in a PA28 is still very different from normal -- 25 vs zero flaps, and rotation/lift-off at significantly lower speed, which gives you a much shorter takeoff roll.

Ron -- I do it that way every time. Flaps and lift-off when the airplane can fly. I find that it keeps me more honest with airplane control as it is a little more mushy and keeps the skills up. I really don't like my wheels on the ground if I don't need them there. Airplanes make terrible race cars.

I set the flaps during the control portion of my run-up and verify they are both equal. I leave them there until I'm in the air. I do the same thing in a 172 or a 150.

 

[jesse]

Jesse, are you presuming that you don't need to do a 180 before taking off? Or are you saying that even if you're going slow enough that you can do a 180 (on a grass runway in the situation I have in mind) it's still beneficial to go right into the roll as you line up?

Other benefits of doing the no-stop method are better cooling of the engine and less chance of pulling rocks into the prop.

If you're doing a 180 on grass, based on my testing, it is faster to do the 180 and go to full power while still in motion. You'll notice that all of my 6Y9 takeoffs were a 180 and then full power without ever stopping. Ed Fred always did the same thing as well and seemed to get good results.

At Gastons -- I never stop either..onto the runway and on with the power.

The down-side is that you are directionally less stable. If you're not that quick with controlling the airplane you might have a loss of directional control by going to full power.

 

[poadeleted20]

Ron -- I do it that way every time. Flaps and lift-off when the airplane can fly.

Then that's a personal choice, not the "Normal Takeoff" procedure in the POH. In any event, I have always felt that aircraft manufacturers are short-changing their customers when they have both Normal and Short-field takeoff procedures in their POH's but provide only "short field" takeoff data. That practice makes it hard for pilots to know when they need to use the short-field procedure, which has slightly elevated risks attached to it as well as often being a bit more white-knuckly for passengers.

 

[rottydaddy]

I notice my POH (Piper Warrior) only has performance charts for short field, and obstacle clearance take off, but not normal take off.

If I'm reading this right, "obstacle clearance takeoff" refers to a normal takeoff... no matter what sort of takeoff, the bottom line is how much room you need to go from a dead stop to 50 ft. AGL (which is the standard "obstacle" height, for whatever reason).

Looking at a '69 Skyhawk POH I have, the chart shows ground roll and distance to clear a 50-foot obstacle, at various weights and with various headwind components and density altitudes...and with a specific "IAS at 50 feet" for each of the three weights shown... but it does say "with flaps up" at the top.
That's either completely different from yours... or basically the same thing.
It seems very odd that they'd only list short-field data in the Piper book... in the case of this Cessna POH, they show you what to expect with no flaps, and it is assumed, I guess, that you will do better with some flaps out (which is normally true).

 

[poadeleted20]

If I'm reading this right, "obstacle clearance takeoff" refers to a normal takeoff... no matter what sort of takeoff, the bottom line is how much room you need to go from a dead stop to 50 ft. AGL (which is the standard "obstacle" height, for whatever reason).

If you look in the Piper POH, I think you'll find that the Piper "obstacle clearance takeoff" is based on use of the short-field/obstacle clearance procedure described in the POH, not the "Normal Takeoff" procedure. And yes, many other manufacturers provide distance charts for both both Normal and Short-Field procedures.

 

[dmccormack]

Other benefits of doing the no-stop method are better cooling of the engine and less chance of pulling rocks into the prop.

Unless you have a CS prop, in which case you can develop "full power" while stopped.

In a fixed pitch prop, sit in the right seat once and see what happens to RPM once you start rolling -- it increases.

 

[gprellwitz]

Unless you have a CS prop, in which case you can develop "full power" while stopped.

In a fixed pitch prop, sit in the right seat once and see what happens to RPM once you start rolling -- it increases.

Dan, maybe I'm missing something here, but I didn't think that the cooling comes from the motion of the prop, but rather from the motion of the plane through the air. So CS/fixed pitch would make no difference in whether you increase cooling flow once moving; they both enjoy that benefit.

 

[dmccormack]

Dan, maybe I'm missing something here, but I didn't think that the cooling comes from the motion of the prop, but rather from the motion of the plane through the air. So CS/fixed pitch would make no difference in whether you increase cooling flow once moving; they both enjoy that benefit.

Sorry -- I was unclear -- you're right: the cooling difference is negligible -- the power difference is significant.

 

[Dave Siciliano]

Well, we all don't perform short field procedures on every takeoff. As a matter of fact, if you start flying a turbocharged plane that is at gross on a hot day, a cruise climb may be necessary to keep CHTs within range and to give reasonable forward vision for other traffic in the climb.

As a matter of fact, I avoid a short field takeoff in the P-Baron. Passengers don't like the 12 degres nose up. If I ever lost an engine on climb, I'd be below or at Vmc with 12 degrees nose up. It would be very difficult to recover. Instead, I lift off with no flaps, accelerate in ground effect to blue line; then, cruise climb. If the field is shorter, I do climb to clear the obstacle; then, lower the nose to cruise climb.

I went out a couple weekends ago with a fella that flies for a major carrier. We researched the POH and did three short field climbs to clear a 50 foot obstacle. It took almost 3,000 feet in the P-Baron and convinced me I never want to put myself in a situation where that is really necessary.

Best,

Dave

 

[jesse]

Well, we all don't perform short field procedures on every takeoff. As a matter of fact, if you start flying a turbocharged plane that is at gross on a hot day, a cruise climb may be necessary to keep CHTs within range and to give reasonable forward vision for other traffic in the climb.

Understand Dave. That is why I referred to a warrior in particular that the OP was asking about -- pointing out that there can be temperature issues on higher performance aircraft.

As a matter of fact, I avoid a short field takeoff in the P-Baron. Passengers don't like the 12 degres nose up. If I ever lost an engine on climb, I'd be below or at Vmc with 12 degrees nose up. It would be very difficult to recover. Instead, I lift off with no flaps, accelerate in ground effect to blue line; then, cruise climb. If the field is shorter, I do climb to clear the obstacle; then, lower the nose to cruise climb.

Different ball-game. A Warrior really doesn't have enough power to not take advantage of all the power it has. I was pointing out that there really isn't a *whole* lot different between a normal takeoff and a short-field takeoff in one. Even if you didn't do a "short field" takeoff in a warrior it would still be a similar value. A "short field" takeoff in a Warrior isn't going to scare anyone either. The only real difference is the addition of some flaps. Also a Vx climbout does not mean short-field either. I don't climb out at Vx unless I'm worried about crashing into something in front of me.

If someone knows nothing about small airplanes -- you'd be surprised the attitudes you can do provided they completely trust you. I've found that I have to be more careful to explain what I'm about to do with another pilot versus a passenger.

What works for me, may not work well for others, I've found though that the more consistent I make my take-offs the better I am at repeating that. Since I have no temperature issues to really worry about it seems most logical to make my consistent take-off short-field which really just means you add flaps and don't drive the airplane on the runway if it can fly.

 

[Skip Miller]

As a point of reference, I have a PA-28-181 POH that has both Flaps Up Ground Roll and a 25* flaps Ground Roll performance charts.

Using Standard Temp, 1000 ft pressure altitude, 2550 lbs take off weight, and no wind for both options:

Flaps up option: Full throttle before brake release, paved level dry runway. Take off distance 1160 feet. Take off speed 53 KIAS. 2050 feet to clear the 50 foot tree.

Flaps 25* option: Full throttle before brake release, paved level dry runway. Take off distance 1000 feet. Take off speed 49 KIAS. 1880 feet to clear the 50 foot tree.

Therefore the short field technique saves 170 feet of runway under these conditions. That's about 8%.

-Skip

 

[jesse]

Therefore the short field technique saves 170 feet of runway under these conditions. That's about 8%.

-Skip

Yup--it isn't really huge. But it's easy to do and has little downsides in such an airplane.