Hot day, max load, should I use flaps on takeoff

[iamtheari]

Here’s my question. Why does my Hershey bar Arrow sound the horn when I retract the gear with two notches of flaps out? That is the POH flap setting for short or soft field takeoffs so it would be nice to be able to use it without training myself to ignore the sound of the gear horn. Are there people trying to land with the gear up and full throttle? Does Piper want me to retract the first notch of flaps before the gear, but ran out of room so they couldn’t write it in the POH?

 

[Huckster79]

I fly a Cessna 140, I pop full flaps once rolling good if I’m in rough surface and it’s an instant jump to a few feet in the air while still quite slow - but climb suffers, the nice thing w the manual flaps is I ease em down by feel of matching acceleration to eliminate a dip from releasing em...

I think the POH always needs to be the base but I’m not convinced it covers every angle, scenario or situation... mine certainly doesn’t but even more modern POHs are legal docs. I don’t think there’s anything wrong with looking for advanced techniques.

POH mentions nothing of on wet grass or soft surface using a lil aileron to pull one tire up n off before the other, borrowing the technique from our float friends to shorten the take off roll..

 

[Snowmass]

I do not fully trust handbooks ever since I found gross errors in compensating for drift in procedure turns in all the official publications. I even wrote an article on this for the "AOPA Pilot" years ago. No doubt flaps increase drag but also increase lift and power available will be greater with less drag but power required will be less with greater lift. If I un-lazy my self maybe I will simply test my plane soon. But, operating off of my dirt airstrip means I will use flaps on the take off run to get off of the rough sooner.

 

[hindsight2020]

Here’s my question. Why does my Hershey bar Arrow sound the horn when I retract the gear with two notches of flaps out? That is the POH flap setting for short or soft field takeoffs so it would be nice to be able to use it without training myself to ignore the sound of the gear horn. Are there people trying to land with the gear up and full throttle? Does Piper want me to retract the first notch of flaps before the gear, but ran out of room so they couldn’t write it in the POH?

I cross referenced POHs for the Arrow II, III, IV and turbo IV. The only one that described that condition as a trigger for the horn was in the -III POH. However, the turbo IV poh finally spelled it out in more detail. Basically it has to do with whether your Arrow came equipped with the backup auto-extender or not. If it did come with the backup extender, then there is no trigger for flaps past 10* with the gear up. That circuit is dedicated to sounding the horn when the auto-extender drops the gear while the switch is still in the UP position. The POH for the turbo IV clarifies that if it didn't come with a backup auto-extender, then that circuit is now dedicated to sounding the horn/beeper for flaps beyond 10* and gear switch in the UP selection. My presumption for the -III POH not providing that caveat, is that no Arrow III S/Ns ever came with the backup extender.

A Hershey bar Arrow is a -II or -I. My Arrow II has the auto extender, and thence doesn't do what yours does, which is in agreement with both the Arrow II POH and the turbo IV description. Never heard of a -II having a circuit for the flaps. Yours is the first I hear of it. I am to assume your Arrow II didn't come with an auto-extender from the factory? If so, that seems in agreement with the description in the turbo IV POH.

 

[iamtheari]

I cross referenced POHs for the Arrow II, III, IV and turbo IV. The only one that described that condition as a trigger for the horn was in the -III POH. However, the turbo IV poh finally spelled it out in more detail. Basically it has to do with whether your Arrow came equipped with the backup auto-extender or not. If it did come with the backup extender, then there is no trigger for flaps past 10* with the gear up. That circuit is dedicated to sounding the horn when the auto-extender drops the gear while the switch is still in the UP position. The POH for the turbo IV clarifies that if it didn't come with a backup auto-extender, then that circuit is now dedicated to sounding the horn/beeper for flaps beyond 10* and gear switch in the UP selection. My presumption for the -III POH not providing that caveat, is that no Arrow III S/Ns ever came with the backup extender.

A Hershey bar Arrow is a -II or -I. My Arrow II has the auto extender, and thence doesn't do what yours does, which is in agreement with both the Arrow II POH and the turbo IV description. Never heard of a -II having a circuit for the flaps. Yours is the first I hear of it. I am to assume your Arrow II didn't come with an auto-extender from the factory? If so, that seems in agreement with the description in the turbo IV POH.

Mine is an Arrow 180 / I, and I believe it came with the auto extender, although that was removed long before my ownership. It is placarded as removed, at any rate. Maybe the removal required adding the horn trigger for flaps 25 and gear up? I’ll have to see if the logbooks contain any clues.

 

[dmspilot]

Mine is an Arrow 180 / I, and I believe it came with the auto extender, although that was removed long before my ownership. It is placarded as removed, at any rate. Maybe the removal required adding the horn trigger for flaps 25 and gear up? I’ll have to see if the logbooks contain any clues.

I was going to say... I did my commercial in an Arrow 180 and don't remember the horn issue you mentioned. But it did have the backup gear extender. Overriding it all the time was a chore.

 

[dmspilot]

I do not fully trust handbooks ever since I found gross errors in compensating for drift in procedure turns in all the official publications. I even wrote an article on this for the "AOPA Pilot" years ago. No doubt flaps increase drag but also increase lift and power available will be greater with less drag but power required will be less with greater lift. If I un-lazy my self maybe I will simply test my plane soon. But, operating off of my dirt airstrip means I will use flaps on the take off run to get off of the rough sooner.

How do procedure turns have anything to do with the topic? And what you wrote next is quite mixed up, power available is not a function of drag and power required does not decrease when lift increases. Just the opposite. Besides, we're talking about climb angles not rates, so the discussion is about thrust available and thrust required, not power.

 

[Checkout_my_Six]

I was going to say... I did my commercial in an Arrow 180 and don't remember the horn issue you mentioned. But it did have the backup gear extender. Overriding it all the time was a chore.

Yup.....same. I did my commercial in an Arrow also.

 

[flyingron]

but....stall speed is reduced with 10 degrees of flaps. So, aren't we making more lift?

As he stated, small amounts of lift increase but also increase and drag. Great on approach, doesn't do much for takeoff performance.

 

[Timbeck2]

1969 Cherokee 140B, 34 gallons fuel, max weight at 2,150 pounds and balance just in. A&P put on a climb prop when the stock prop was red tagged a few years ago at annual. Airport elevation 49 feet MSL. Temperature was 95 and density altitude 2,200. As expected with 150Hp the climb out at 85MPH was anemic at a tad over 500 FPM. Would taking off with 1 or 2 notches of flap be prudent and improve the climb out even though the POH does not suggest it as a hot day procedure?

49' airport elevation, OVER 500 fpm climb rate in a Cherokee 140? I fail to see the problem here.

 

[unsafervguy]

<flame suit on> i find it interesting that a bunch of internet people think they know better that the engineers, and test pilots that designed, built, and documented and validated the performance data for the FAA. bottom line, fly it the way the book says.

 

[Ravioli]

<flame suit on> i find it interesting that a bunch of internet people think they know better that the engineers, and test pilots that designed, built, and documented and validated the performance data for the FAA. bottom line, fly it the way the book says.

This from a guy who built an airplane in his garage? Yah, it's fine for you to write YOUR OWN book but not the guys who can afford certificated planes?

[That be a joke, for those who may not know]

 

[dtuuri]

Hot here with 2000’ DAs at sea level. Leaning for takeoff improved RPMs by almost 250, which means a lot more power. That’s more important than a notch of flaps.

And this doesn't melt your valves?

 

[Snowmass]

How do procedure turns have anything to do with the topic? And what you wrote next is quite mixed up, power available is not a function of drag and power required does not decrease when lift increases. Just the opposite. Besides, we're talking about climb angles not rates, so the discussion is about thrust available and thrust required, not power.

Reading comprehension again. It's obviously not the procedure turns but the fact that ALL the expert sources were in error so I actually did something dangerously radical and tested these claims and after finding all the experts were in error I then redid the math which was verified by a professor of mathematics. So, once again One test is worth 1000 opinions.

 

[dmspilot]

Reading comprehension again.

So you didn't actually write "power available will be greater with less drag but power required will be less with greater lift" which is completely wrong?

Because some book said something about procedure turns you allege as being incorrect, means POH procedures are incorrect. That's poor use of logic, not poor reading comprehension.

 

[iamtheari]

I was going to say... I did my commercial in an Arrow 180 and don't remember the horn issue you mentioned. But it did have the backup gear extender. Overriding it all the time was a chore.

I am (finally) finishing up my commercial and have a great appreciation for the prior owner who had the auto extender removed. The horn is a nuisance but at least it’s not actively trying to kill me.

 

[455 Bravo Uniform]

It would help to see all this in graph form. Distance on X axis, altitude on Y axis, and a profile for each configuration (flaps, weight) with time. Std conditions. With actual data.

 

[steingar]

This one isn't difficult. You look at your POH, or whatever you've got. You're at gross, and not over, RIGHT? If so, you look up your performance for those conditions or something similar. Either you have it and you go, or you don't and you stay. Had this very issue with a landing the other day at a strip that was shorter than what I've done in the past. Book said I could do it under the conditions with a sizable margin, off I went. Turned out to be a nothing burger getting in and out, and I had a great day.

 

[Snowmass]

Because some book said something about procedure turns you allege as being incorrect, means POH procedures are incorrect. That's poor use of logic, not poor reading comprehension.

My 1964 C-210 Owers Manual (no POH exists) states to use 20 degrees flaps and to climb at 63 MPH until all obstacles are cleared. Do you comprehend all obstacles? It does not say 10 foot nor 50 foot obstacles but all.

And I did not allege an error in all instrument flying books I could find but proved the error by actual testing, calculated the proper procedure, and had my calculations verified by a professor of mathematics at the University of Illinois to the satisfaction of the AOPA.

Try again.

 

[dmspilot]

Do you comprehend all obstacles? It does not say 10 foot nor 50 foot obstacles but all.

What is this supposed to be a counterpoint to?

And I did not allege an error in all instrument flying books I could find but proved the error by actual testing, calculated the proper procedure, and had my calculations verified by a professor of mathematics at the University of Illinois to the satisfaction of the AOPA.

Next you can have your personality complex verified by a professor of psychology at the University of Illinois to the satisfaction of the APA. Good luck.

 

[unsafervguy]

This from a guy who built an airplane in his garage? Yah, it's fine for you to write YOUR OWN book but not the guys who can afford certificated planes?

[That be a joke, for those who may not know]

sorry, mine was built in a hangar..........

 

[UngaWunga]

1969 Cherokee 140B, 34 gallons fuel, max weight at 2,150 pounds and balance just in. A&P put on a climb prop when the stock prop was red tagged a few years ago at annual. Airport elevation 49 feet MSL. Temperature was 95 and density altitude 2,200. As expected with 150Hp the climb out at 85MPH was anemic at a tad over 500 FPM. Would taking off with 1 or 2 notches of flap be prudent and improve the climb out even though the POH does not suggest it as a hot day procedure?

How long is the runway? Do you have room to use the proper amount of flaps to get off the ground, and then stay in ground effect to pick up a little speed before climbing out?

 

[danhagan]

As expected with 150Hp the climb out at 85MPH was anemic at a tad over 500 FPM.

49' airport elevation, OVER 500 fpm climb rate in a Cherokee 140? I fail to see the problem here.

Tim and I are in the desert with HIGH DA. Training in a C-152 in summer with the CFI on board, you'd be lucky getting over 150 FPM ... CFI used to call for a go-around just as the tires touched, which usually resulted in trying to climb and re-settling to the runway a second time - great learning experience. Did hit a down draft on departure once that was a real eye opener. My first purchase post PPL (The Tiger) seemed like greased lightening to me in comparison, and now the RV7 is more of a "whoa big fella" deck angle when at Vx.

 

[Salty]

Flaps on GA airplanes will NEVER better Vx or Vy.

They will decrease the distance needed to climb over "close-in" obstacles. But once the close in obstacles are cleared, a clean wing will give Vx and Vy.

I dunno about anyone else, but I'm confused by the use of Vx and Vy in this thread. Not just in this post, but throughout. It seems like Vx and Vy are being used to describe angles and rates of climb, but they are airspeeds. They will likely be different with flaps in different configurations. And using flaps may or may not result in better or worse angles and rates of climb, and Vx and Vy may change as well, but I have no idea for certain.

 

[dtuuri]

I dunno about anyone else, but I'm confused by the use of Vx and Vy in this thread. Not just in this post, but throughout. It seems like Vx and Vy are being used to describe angles and rates of climb, but they are airspeeds. They will likely be different with flaps in different configurations. And using flaps may or may not result in better or worse angles and rates of climb, and Vx and Vy may change as well, but I have no idea for certain.

In all the POH's I've seen (and Part 25 airplanes too) flaps decrease angle of climb and shorten takeoff roll.

 

[Salty]

In all the POH's I've seen (and Part 25 airplanes too) flaps decrease angle of climb and shorten takeoff roll.

If you shorten takeoff roll, wouldn't that be an increased angle of climb?

 

[hindsight2020]

I dunno about anyone else, but I'm confused by the use of Vx and Vy in this thread. Not just in this post, but throughout. It seems like Vx and Vy are being used to describe angles and rates of climb, but they are airspeeds. They will likely be different with flaps in different configurations. And using flaps may or may not result in better or worse angles and rates of climb, and Vx and Vy may change as well, but I have no idea for certain.

Yes they're both airspeeds. They correspond to angle of climb, and rate of climb, respectively. Yes, changes in weight, density altitude and configuration (gear and camber of the wing), will alter the value of both. POHs and airplane manuals are written for the lowest common denominator. As such, generalizations and single-value definition are utlilized, patronizing as it may seem to some. I respectfully offer this thread as evidence of why OEMs behave in such ways. Don't shoot the messenger.

As to angle of climb: The cambering of subsonic, moderate to high aspect ratio unswept wings via flap defelction, WILL result in a decrease (that's a lowering, as in bad) of the angle of climb, due to increased drag imparting a cost on excess thrust otherwise available when the wing is clean. People's misunderstanding of the roles of wing lift versus aircraft thrust in climbing flight is why this seems to be a topic of confusion. to take generalizations made by POHs for the sake of simplifying takeoff technique for the lowest common denominator should not be taken as evidence of the contrary.

If you shorten takeoff roll, wouldn't that be an increased angle of climb?

Absolutely not.

 

[Salty]

Yes they're both airspeeds. They correspond to angle of climb, and rate of climb, respectively. Yes, changes in weight, density altitude and configuration (gear and camber of the wing), will alter the value of both. POHs and airplane manuals are written for the lowest common denominator. As such, generalizations and single-value definition are utlilized, patronizing as it may seem to some. I respectfully offer this thread as evidence of why OEMs behave in such ways. Don't shoot the messenger.

As to angle of climb: The cambering of subsonic, moderate to high aspect ratio unswept wings via flap defelction, WILL result in a decrease (that's a lowering, as in bad) of the angle of climb, due to increased drag imparting a cost on excess thrust otherwise available when the wing is clean. People's misunderstanding of the roles of wing lift versus aircraft thrust in climbing flight is why this seems to be a topic of confusion. to take generalizations made by POHs for the sake of simplifying takeoff technique for the lowest common denominator should not be taken as evidence of the contrary.
View attachment 87391





Absolutely not.

Help me out here. If I climb with flaps to 1 foot in 100 feet along the runway that's a 1:100 climb, if I'm still on the ground without flaps, that's a 0:100 climb. With flaps, my climb angle was greater.

 

[Pilawt]

Different airplanes, different procedures. The rate-of-climb and "time, distance and fuel to climb" charts in the PA-32-260 and PA-32-300 handbooks are based on 10° flap. Some owners leave a notch of flap in all the way up to cruising altitude. (I haven't flown a straight-wing PA-32 enough to investigate it, so I'm not endorsing that technique one way or the other.)

 

[dmspilot]

"However, if the obstacle is a relatively short distance from the takeoff point, the additional distance required to accelerate to [Vx for flaps 0°] may be detrimental and the resulting situation may prove to be a short term gain problem. In this case, it may prove necessary to begin climb out at or near the takeoff speed or hold the aircraft on the runway for extra speed and a subsequent zoom. The problem is sufficiently varied that no general conclusion can be applied...particular procedures are specified for each aircraft in the [POH]."

Aerodynamics for Naval Aviators (Edited slightly to remove references to jets.)

 

[William Pete Hodges]

1969 Cherokee 140B, 34 gallons fuel, max weight at 2,150 pounds and balance just in. A&P put on a climb prop when the stock prop was red tagged a few years ago at annual. Airport elevation 49 feet MSL. Temperature was 95 and density altitude 2,200. As expected with 150Hp the climb out at 85MPH was anemic at a tad over 500 FPM. Would taking off with 1 or 2 notches of flap be prudent and improve the climb out even though the POH does not suggest it as a hot day procedure?

I have about 500 hours in a 1968 Cherokee 140, 160 HP upgrade, and climb prop. Mine had the trim crank on the ceiling. The POH for the older airplanes listed normal, soft field, and short field procedures. Not specifically a hot field procedure, but I do some flying out of a 2100 ft grass strip, so I used the short field procedure all the time. For soft field 1 notch of flaps to keep the nose light then snap in the second notch at rotate speed. If there is crosswind increase the ground roll 5mph or so with no flaps on a hard surface, then snap in 2 notches of flaps and that bird will leap off of the runway like it was shot out of a cannon. On a hot day use the same procedure referring to the same airpeed numbers. Your ground roll will be a lot longer (look it up) and your rate of climb will be less (look that up too) but your bird will fly the same, just not as robust as you're used to.

PS I really did like the 140. An excellent airplane but a little underpowered on hot days. Still, I successfully flew it to and from 2e8 8 times over the years in the late summer with my wife and dog and all the necessary stuff for a week.

 

[jonvcaples]

Using flaps for take-off will shorten ground roll. Unfortunately, it will typically cut rate and angle of climb. Most piston GA aircraft do not have sufficient performance prediction information (nor do we as pilots have access to obstacle data) to estimate performance for a given set of conditions.

With twins we also have to consider Vmc. Some pilots will ignore it so they can use shorter runways not a good or recommended idea.

 

[cowman]

On the Lance I put in one notch of flaps for standard takeoff. This is not the normal procedure but I had several recommendations to try it and I found it to make for a smoother and more predictable rotation. Never really looked at ground roll or climb performance. I just like the feel of it better.

On the subject of Vx and Vy, here's how I always understood it in my own head- Vy is the most efficient climbing speed(best rate). What Vx does is slow down your forward motion to give you more time to climb over an obstacle ahead such as trees... so your overall climb rate is slower in the sense of feet/min but since you're covering ground slower you can gain more altitude in a given horizontal distance.

 

[dtuuri]

If you shorten takeoff roll, wouldn't that be an increased angle of climb?

I'll answer with a question of my own, "Since full flaps result in the slowest flying and lift-off speed, wouldn't the plane climb steeper?"

 

[kgruber]

Different airplanes, different procedures. The rate-of-climb and "time, distance and fuel to climb" charts in the PA-32-260 and PA-32-300 handbooks are based on 10° flap. Some owners leave a notch of flap in all the way up to cruising altitude. (I haven't flown a straight-wing PA-32 enough to investigate it, so I'm not endorsing that technique one way or the other.)

View attachment 87392

Maybe. But that would be in conflict with the written Vy configuration in section III of the Piper Cherokee 6 B owner's Handbook. Note: It doesn't say "retract the flaps to 10°.
http://www.mattbeyer.com/poh/PA-32-260-Cherokee6-POH.pdf

 

[William Pete Hodges]

I'll answer with a question of my own, "Since full flaps result in the slowest flying and lift-off speed, wouldn't the plane climb steeper?"

The Cherokee 140 is rated to climb max angle with 2 notches of flaps. Full flaps is too much drag and it is not rated to climb with full flaps. The split flap used on the Cherokee is very effective because it channels high pressure air from under the wing to the upper surface of the flap. (It is simple to build too.) That faster air sucks the air off of the back of the wing and increases adhesion of air on the wing in the latter half of the wing cord during the climb. It is a good system.

 

[kgruber]

The Cherokee 140 is rated to climb max angle with 2 notches of flaps...........

But only to clear "close-in" obstacles. Once clear of those the flaps are retracted and climb at Vx, Vy, or Vcc

 

[Salty]

But only to clear "close-in" obstacles. Once clear of those the flaps are retracted and climb at Vx, Vy, or Vcc

How does the plane know to start climbing at a lower angle after it gets past the close in obstacles?

Vx is the airspeed that will result in the best angle of climb whether you are close to an obstacle or not.

 

[William Pete Hodges]

How does the plane know to start climbing at a lower angle after it gets past the close in obstacles?

Vx is the airspeed that will result in the best angle of climb whether you are close to an obstacle or not.

The airplane doesn't, the pilot does. The pilot controls the airplane so it becomes an extension of his body. All that is required is practice, attention to detail, improvement, and more practice. The idea is to wear your airplane like a suit of clothes so it responds to your mind without thinking about it.

You are going to make mistakes as you learn. Look at them honestly during your post flight review and figure out how to do it without the mistake. Then add that tweak to your flying. Over time you'll make fewer and fewer mistakes and become a better pilot. One day you'll be wearing your airplane like a suit of clothes.

Have FUN. Fly SAFE

 

[Salty]

The airplane doesn't, the pilot does. The pilot controls the airplane so it becomes an extension of his body. All that is required is practice, attention to detail, improvement, and more practice. The idea is to wear your airplane like a suit of clothes so it responds to your mind without thinking about it.

You are going to make mistakes as you learn. Look at them honestly during your post flight review and figure out how to do it without the mistake. Then add that tweak to your flying. Over time you'll make fewer and fewer mistakes and become a better pilot. One day you'll be wearing your airplane like a suit of clothes.

Have FUN. Fly SAFE

You missed the point. Vx is Vx is Vx. It doesn’t change because you are close to an obstacle.

you may not want to fly Vx after you clear the obstacle, but that’s not what he said. He said remove flaps and fly Vx if you want to.

more importantly, if the poh says max angle of climb is 2 notches of flaps then clearly flaps are increasing max angle of climb. Seems obvious to me, but it seems to have been missed.