Higher Vr speed?

[ettsn]

I'm a little embarrassed to ask this, as it's something I feel like I should know already, but can't seem to find an answer elsewhere.

In my Cherokee 140 POH, Vr is an IAS of 60mph. If I rotate then, it climbs very lethargically. I've found that if I wait until more like 70mph, it comes off the ground better and will much more quickly and easily accelerate to either Vx or Vy.

Is there any danger or harm in delaying rotation until slightly faster? I can't think of anything, except slightly reduced runway in case of emergency. What am I missing?

 

[MauleSkinner]

What airspeed are you trying to climb at, and how does this compare to Vx or Vy?

My guess I'd you're expecting the airplane to lift off at rotation...the intent of a rotation speed is to establish an attitude such that when the airplane is ready to fly, it will...and usually at the proscribed climb speed.

 

[Stingray Don]

Instead of rotating at 70 KIAS you could rotate at 60 KIAS and accelerate in ground effect before climbing out.

 

[ettsn]

Vx is 74mph, Vy is 85mph. I generally climb somewhere between the two.

Fully understand that rotate speed isn't liftoff speed, I get that. And when I rotate at 60mph, once it lifts, it absolutely accelerates in ground effect. Just considerably more slowly than if I hold the nose for a few more seconds.

So maybe what I'm feeling is more about the transition from rotate to liftoff, and the shortened time to Vx (since I'm already going faster -- almost Vx)? Perhaps it's my imagination, but even the climb after liftoff feels stronger if I delay rotation.

I'm sure the typical density altitude here in Georgia doesn't help either!

 

[fiveoboy01]

I rotate at the POH recommended speed and pitch to get the acceleration and in turn the V speed I would like.

I'm not a fan of rolling at speed on the runway any longer than I need to. Airplanes fly better than they drive.

If there is a strong crosswind, I will add 5-10 knots to the rotation speed.

 

[Henning]

It's a matter of forward distance or time covered to get to an altitude. Letting it fly off when it wants and and accelerate to Vx and keep it there will get you to the height in the shortest distance, if you allow it to accelerate to Vy once it flies off it will get there in the least time.

Doing 'zoom climb' maneuvers are more fun, but don't gain any efficiency.

 

[dtuuri]

I'm a little embarrassed to ask this,...

In my Cherokee 140 POH, Vr is an IAS of 60mph. <snip>

Ugh, there's that word again, "rotate". Just use back pressure to lift the nose wheel off the ground as you begin to add power. When it responds, relax it enough to hold the attitude and wait for the plane to leave the ground smoothly. No need to "rotate".

dtuuri

 

[fiveoboy01]

A friend likes to accelerate to 100-110 knots then zoom climb to TPA on takeoff. His justification is that if the engine fails, he's either close to the runway, or up at TPA and spending less time in the climb. No idea if his theory or method is valid, and he doesn't always do it... but it's fun to ride along haha.

 

[fiveoboy01]

Ugh, there's that word again, "rotate". Just use back pressure to lift the nose wheel off the ground as you begin to add power. When it responds, relax it enough to hold the attitude and wait for the plane to leave the ground smoothly. No need to "rotate".

dtuuri

The airplane is still rotating, even with that method. Sorry that you don't like the word.

 

[ejensen]

Ugh, there's that word again, "rotate". Just use back pressure to lift the nose wheel off the ground as you begin to add power. When it responds, relax it enough to hold the attitude and wait for the plane to leave the ground smoothly. No need to "rotate".

dtuuri

^this. The plane will fly when it's ready.

 

[Henning]

Ugh, there's that word again, "rotate". Just use back pressure to lift the nose wheel off the ground as you begin to add power. When it responds, relax it enough to hold the attitude and wait for the plane to leave the ground smoothly. No need to "rotate".

dtuuri

Yep, if you just roll the trim up for Vy, most singles will fly off on best profile without doing anything.

 

[Henning]

The airplane is still rotating, even with that method. Sorry that you don't like the word.

There is a difference between the plane rotating while reaching energy equilibrium and you 'rotating' the plane. Typically you only need to 'rotate', i.e. pull back, to make the plane start to climb in ME aircraft. Typically they are set up with neutral/negative AOA on the wheels so they do not fly off between stall and Vmc, you literally have to haul back to get the nose up and the plane started up. If you have most SE planes trimmed correctly for climb, they will just fly off when ready and transition through a nice acceleration profile out of ground effect.

 

[fiveoboy01]

What about trimmed for takeoff?

Is the aircraft still rotating about the main gear axis?

 

[neilki]

Remember all your takeoff & climb performance numbers are based on rotating at VR...

 

[Henning]

What about trimmed for takeoff?

Is the aircraft still rotating about the main gear axis?

It isn't rotating at all until after flying. Look at the picture of your airplane, look at the AOA of the wing, it will float itself off the runway when speed becomes sufficient.

 

[AggieMike88]

A friend likes to accelerate to 100-110 knots then zoom climb to TPA on takeoff. His justification is that if the engine fails, he's either close to the runway, or up at TPA and spending less time in the climb. No idea if his theory or method is valid, and he doesn't always do it... but it's fun to ride along haha.

I take it you've not seen EdFred Productions video on Zoom Climb versus Vy?

It was intended as a poke at a PoA member who owns an RV-8a, but still makes the point.

And is funny as all get out too. Link to Video

 

[Dead Stick]

Holding it on the ground past Vr is a poor practice and one that not all aircraft tolerate well. It's always best to just follow the procedures given in the POH or aircraft handbook.

 

[fiveoboy01]

It isn't rotating at all until after flying. Look at the picture of your airplane, look at the AOA of the wing, it will float itself off the runway when speed becomes sufficient.

I'll stand corrected then, as I assumed all tricycle gear aircraft have a negative angle of attack whilst sitting on the ramp.

Either way, I'll probably still use the term rotate

 

[Henning]

I'll stand corrected then, as I assumed all tricycle gear aircraft have a negative angle of attack whilst sitting on the ramp.

Either way, I'll probably still use the term rotate

They actually can if the struts aren't properly serviced, but if you have it trimmed correctly, the wings and tail will have it in the correct posture before flying speed. There are some SE planes though that heavy at the front of the CG envelope will need you to add some pull to get the nose up.

Thing is, if you have to 'rotate' you really need to modify your T/O trim. That's why people hate hearing that term.

 

[fiveoboy01]

I take it you've not seen EdFred Productions video on Zoom Climb versus Vy?

It was intended as a poke at a PoA member who owns an RV-8a, but still makes the point.

And is funny as all get out too. Link to Video

That was amusing. My uncle has a 4 and an 8. I'm not sure he's got that same attitude but he does do some zoom type manuevers. He flew the F4 though, so I think he can get away with that

 

[AggieMike88]

I'll stand corrected then, as I assumed all tricycle gear aircraft have a negative angle of attack whilst sitting on the ramp.

Next time you're at the airport, take a side look at a Cessna 152/172/182. When on level ground, they have a slight nose up pitch. This is also evident when the attitude indicator's gyro has spun up. In N55WB, it's about 1/2-dot up.

I made the mistake in early transition to reset the AI's "little airplane" to the horizon when in the runup area. Then wondered why when I showed level on the AI, I was in a slight descent. Now I don't do that, and cross check "pitch + power = performance" numbers as I depart and then check the AI reference once in level cruise.

 

[Henning]

That was amusing. My uncle has a 4 and an 8. I'm not sure he's got that same attitude but he does do some zoom type manuevers. He flew the F4 though, so I think he can get away with that

Everybody does them for fun, no worries. The problem comes when people start trying to tout the performance gains from it which don't exist. The advantages are purely visceral, or you're in an F-15 doing a vertical 'noise abatement' climb.

 

[fiveoboy01]

I made the mistake in early transition to reset the AI's "little airplane" to the horizon when in the runup area. Then wondered why when I showed level on the AI, I was in a slight descent. Now I don't do that, and cross check "pitch + power = performance" numbers as I depart and then check the AI reference once in level cruise.

I used to set it on the ground too and then realized once airborne it was wrong.

For some reason I never did make the connection as to why, until now. Oops.

I still set it in the middle on the ground as this gets it "close enough" and as you said I pitch for a certain airspeed anyways. I normally click the autopilot on and then tweak it to where it needs to be.

 

[Graueradler]

Ugh, there's that word again, "rotate". Just use back pressure to lift the nose wheel off the ground as you begin to add power. When it responds, relax it enough to hold the attitude and wait for the plane to leave the ground smoothly. No need to "rotate".

dtuuri

You will reach Vr quicker if you accelerate with zero AOA until reaching Vr. By holding the nose up beginning with power application, you are generating lift/drag during acceleration before lift is needed.

 

[Henning]

You will reach Vr quicker if you accelerate with zero AOA until reaching Vr. By holding the nose up beginning with power application, you are generating lift/drag during acceleration before lift is needed.

Look at the realities of the L/D graph. If you just let the trim do the job, you lose nothing of measurable significance. I didn't see where anyone was proposing to hold the nose up early except for a soft field T/O.

 

[MauleSkinner]

Remember all your takeoff & climb performance numbers are based on rotating at VR...

Here's probably one of the key issues...Vr is really only applicable if you're trying to replicate "book" performance and techniques, and "book" performance is only applicable to short field takeoff and landing technique. This isn't "normal" for most people.

 

[Fearless Tower]

The airplane is still rotating, even with that method. Sorry that you don't like the word.

The issue isn't so much with the word itself, but that some put too much emphasis on the physical rotation.

For the OP, it sounds like you may be over-rotating/trying to force it off the ground before it is ready to fly.

Just because you reach the Vr, doesn't mean that it is going to automatically leave the ground. Try easing the yoke back slightly at Vr and let the airplane fly off when it is ready. That may or may not be your problem, but worth a try.

 

[Henning]

Here's probably one of the key issues...Vr is really only applicable if you're trying to replicate "book" performance and techniques, and "book" performance is only applicable to short field takeoff and landing technique. This isn't "normal" for most people.

No, not really. There are specific "short" and "soft" techniques that may differ slightly from "normal" by trading one safety or drag margin for another. Normal technique is usually determined around 'normal' circumstances. In a single engine plane though, there are really only two correct profiles to fly off the runway and that is either start flying when the plane will and accelerate to either Vx or Vy until you get to an altitude from which you can make a landing. Anything other than that and you give up a margin of safety.

 

[ejensen]

Is Vr even published for light singles? I just checked the manuals for a C177rg and a Cherokee 180G. Founds nothing about Vr. The Cherokee manual says:
"Allow the airplane to accelerate to 50 -60 mph, then ease back on the wheel enough to let the airplane fly itself off the ground. "

 

[MauleSkinner]

No, not really. There are specific "short" and "soft" techniques that may differ slightly from "normal" by trading one safety or drag margin for another. Normal technique is usually determined around 'normal' circumstances. In a single engine plane though, there are really only two correct profiles to fly off the runway and that is either start flying when the plane will and accelerate to either Vx or Vy until you get to an altitude from which you can make a landing. Anything other than that and you give up a margin of safety.

Technique for max safety margins can vary tremendously, and are very subjective.

"Book numbers", on the other hand, can only be replicated using "book technique". Since there are no "book numbers" for soft field technique, the only "book numbers" available are for short field technique, and that is the technique that uses a published rotation speed.

My assertion is that neither of these are necessary to most pilots' day to day operations. Are you agreeing or disagreeing? You're post isn't clear on that.

 

[orange]

The planes that I trained on and rent (Cherokee 160) require some back pressure to lift off the ground. I was trained to trim NUETRAL (not nose down nor up) for take off. However I always trim about one turn nose down from neutral. If I trim neutral, they will get off the ground easy but then try to zoom up, bleeding off airspeed and takes some force forward on the yoke to keep within Vy or a little less. I'm not looking to demonstrate a departure stall 100 feet over the runway.

 

[fiveoboy01]

Is Vr even published for light singles? I just checked the manuals for a C177rg and a Cherokee 180G. Founds nothing about Vr. The Cherokee manual says:
"Allow the airplane to accelerate to 50 -60 mph, then ease back on the wheel enough to let the airplane fly itself off the ground. "

The manual for the Archer says Accelerate to 52 to 65 KIAS, Control wheel - back pressure to rotate to climb attitude.

I've not flown everything but the Archer requires significantly more aft yoke pull than the 172 to get it flying.

 

[ejensen]

The manual for the Archer says Accelerate to 52 to 65 KIAS, Control wheel - back pressure to rotate to climb attitude.

I've not flown everything but the Archer requires significantly more aft yoke pull than the 172 to get it flying.

Yeah, kind of hard to define what rotate mean to each pilot. I think of it as a real pull on the yoke not just a little back pressure. How you're trimmed makes a difference too.

 

[Henning]

The 'numbers' are aerodynamic numbers, they do not change except with change in flaps, then those numbers are specified. Vx and Yy are calculated by gross weight, not surface or circumstance. If you want the BEST rate or angle of climb, those are the numbers you establish once you come off the ground. The only difference in techniques is how to handle the ground roll and acceleration to flying speed. Once the wheels are off the ground, it's all the same.

 

[Henning]

The planes that I trained on and rent (Cherokee 160) require some back pressure to lift off the ground. I was trained to trim NUETRAL (not nose down nor up) for take off. However I always trim about one turn nose down from neutral. If I trim neutral, they will get off the ground easy but then try to zoom up, bleeding off airspeed and takes some force forward on the yoke to keep within Vy or a little less. I'm not looking to demonstrate a departure stall 100 feet over the runway.

It pitches up, but that is because it is still accelerating. If you trim for Vy, it will stabilize on Vy. It's not 'bleeding off airspeed', watch it, it is accelerating climb at best rate. If it's short, give it the reigns to climb.

Trim controls forward speed, power controls vertical speed. The key to flying "like a pro" is to make the plane do the flying.

 

[fiveoboy01]

Yeah, kind of hard to define what rotate mean to each pilot. I think of it as a real pull on the yoke not just a little back pressure. How you're trimmed makes a difference too.

Yesterday I did a localizer approach culminating in a touch and go. You generally don't have time to flick the trim wheel on the go, or you forget.

Takes even more back pressure to get the dumb plane off the ground in that instance

 

[Henning]

Yesterday I did a localizer approach culminating in a touch and go. You generally don't have time to flick the trim wheel on the go, or you forget.

Takes even more back pressure to get the dumb plane off the ground in that instance

Huh, I always found that if I had a PA-28 trimmed right for landing, it flew off pretty well when I dumped the flaps and added throttle.

 

[MauleSkinner]

The 'numbers' are aerodynamic numbers, they do not change except with change in flaps, then those numbers are specified. Vx and Yy are calculated by gross weight, not surface or circumstance. If you want the BEST rate or angle of climb, those are the numbers you establish once you come off the ground. The only difference in techniques is how to handle the ground roll and acceleration to flying speed. Once the wheels are off the ground, it's all the same.

Ah...I see the confusion...the "numbers" I was referring to are takeoff and landing distances published in the AFM/equivalent. I should've been more clear.

 

[Cpt_Kirk]

Ugh, there's that word again, "rotate". Just use back pressure to lift the nose wheel off the ground as you begin to add power. When it responds, relax it enough to hold the attitude and wait for the plane to leave the ground smoothly. No need to "rotate".

dtuuri

You've said it all.

 

[JOhnH]

I assume you are sure that your POH lists Vx as mph instead of its?