Is rotation closer to Vx, than Vr necessarily a bad idea?

T

tobnpr

Pre-takeoff checklist
Joined
Aug 29, 2022
Messages
128
Location
Lakeland, FL
Display Name
Display name:
tobnpr
Taking lessons in a PA-28-180.
In the first pre-flight briefing, my CFI told me that I should rotate at 80 mph. When I questioned why- when Vr is 60 mph- he told me that the plane is "happier" rotating at 80, but no problem rotating at 60 if that's what I wanted to do.

At 80, it took very light backpressure on the yoke to rotate and get airborne ("happy")- definitely no "forcing" the aircraft to stay on the runway prior to reaching 80. Assuming adequate runway (which we have), anyone disagree with this, and if so, why?
 
More induced drag early means slower acceleration and while you might get off of the ground sooner (for ex for short field), overall time/distance to climb to a certain altitude is slower. Also, Vr is closer to Vg and Vy, one of which you are trying to get to (Vy if you’re headed out; Vg if you lose the engine).
 
DOTS - Depends on the Situation. Too gusty & too slow & you might stop flying & settle. Lots of runway? Why not build some speed? I’m not a low wing guy, but even with a high wing I prefer to get off as soon as I can, lower the nose, & accelerate slightly in ground effect. I’m told that happens even better in a low wing aircraft. It’s that tire scrubbing, not quite driving — not quite fly monument that has always felt squirrelly to me.
 
POH says 50 to 60 mph. You do have to pull back harder but I don’t find that the pa28-180 is less inclined to climb or accelerate if you pull back at 60mph. I mean that plane will climb with full flaps unlike less powerful versions (for me and my fly weight CFI on board with 2/3 fuel).

Usually when you pull back at 60 it’s pretty much at 80 by the time the plane is a few feet off the ground.

And for short field etc the POH says additionally 25 flaps. Rotation is still 50-60.

I personally find that I miss 50 and pull back at 60 cause it takes such a short time to get up to speed.

I would experiment and see what results in the quickest to altitude. You want to be as high as possible in the shortest time and distance from the field. In case your engine conks out, that height is your energy to find a landing spot. If you are at 1000 agl within a mile of the airport you are in a good position to turn back and glide back to the runway.

That said right now your CFI might just be asking you to go to 80 first so you are that much further from stall. When he gets more comfortable with you and you do short field likely you’ll be asked to rotate at 60.
 
Last edited:
^^^^ Agree with this.
But, primarily, if you want your take-off distance to match what the POH says, then lift the nose at the specified airspeed.

I'm noticing that many newer flight instructors want to see faster speeds than specified in the POHs. Not just for rotation, but for approach as well. Not sure what's going on but am believing they've become wimps of some sort. Anyone else noticing this? Any insight?
 
My habit in most small GA aircraft is to start gently raising the nose slightly as the airspeed approaches the bottom of the white arc, then let the plane get airborne when it’s ready. Seems to result in a Vy climb or thereabouts. Gusty or really windy, I’ll leave it on the ground just a bit longer. But a Cherokee 180 should be ready to fly well before 80 mph.

Note: Rotate does NOT mean the speed you pull the plane into the air - just rotate it gently around its lateral axis and wait.
 
tobnpr said:
Taking lessons in a PA-28-180.
In the first pre-flight briefing, my CFI told me that I should rotate at 80 mph. When I questioned why- when Vr is 60 mph- he told me that the plane is "happier" rotating at 80, but no problem rotating at 60 if that's what I wanted to do.

At 80, it took very light backpressure on the yoke to rotate and get airborne ("happy")- definitely no "forcing" the aircraft to stay on the runway prior to reaching 80. Assuming adequate runway (which we have), anyone disagree with this, and if so, why?
Click to expand...

Unless your are doing a soft/short takeoff, or there is a stiff cross wind, just set the trim correctly and let the airplane fly off by itself.
 
FastEddieB said:
Note: Rotate does NOT mean the speed you pull the plane into the air - just rotate it gently around its lateral axis and wait.
Click to expand...

I was going to post this as well. I suspect there might be a misunderstanding of what rotation means by either the instructor or student. Assuming this is the problem, once things are sorted out a better technique might follow.
 
Keep in mind that the longer you keep the plane on the ground, the more wear and tear on the mechanical parts of the wheels and such. There's nothing particularly dangerous about taking off at normal speeds as published in the POH and accelerating in ground effect.

I think your CFI is "interesting."
 
You'll get a feel for it. A cherokee takes a good firm pull to get off the ground at the book rotation speed, and you'll stall it if you don't reduce that back pressure once she's off the ground. I've become a fan of the firm pull to break the ground and let her accelerate in ground effect. Significantly shorter ground roll, and I feel like you get to Vy faster. It's hard to convince yourself it's okay to pull that hard at first.

Second fastest is to let her accelerate on the ground and basically fly off on her own like your cfi suggests. I feel like the plane gets squirrelly and hard to control at higher speeds though, and with cherokees your front wheel is connected to your rudder, which exacerbates this issue in a crosswind.

The worst of both worlds IMO is doing a light pull and pulling the nose off and wheelying down the runway. That solves the nosewheel steering issue, but the induced drag slows your acceleration and increases ground roll significantly.
 
There are "procedures" and there are "techniques." The owner's manual or POH gives you the procedures, things you must do. Your CFI may give you some other techniques, other ways you can do. Experiment and see what works best for you.
 
My philosophy is to get the airplane off the ground and climbing as soon as possible in order to have as much altitude as possible in the event of a LOTOT.

Any extra speed beyond Vx or Vy is wasting energy that could be used to get to altitude sooner and provide a few more seconds to make a successful emergency landing in a single engine airplane.

Do what the POH says and adjust for conditions once you see what the preferred technique looks like.
 
noahfong said:
^^^^ Agree with this.
But, primarily, if you want your take-off distance to match what the POH says, then lift the nose at the specified airspeed.

I'm noticing that many newer flight instructors want to see faster speeds than specified in the POHs. Not just for rotation, but for approach as well. Not sure what's going on but am believing they've become wimps of some sort. Anyone else noticing this? Any insight?
Click to expand...

When I learned in the Arrow I was taught 100mph on approach, now I slow it down to 78mph (basically 80mph) because well difficult to see the exact airspeed on a manual gauge.
 
I’ve played around with this and still haven’t perfected it, and I am thankful for more runway then what’s needed. On shorter runways if you do not pull the gear up you’ll find yourself quickly approaching the tree line in front and having difficulty gaining altitude. I rotate or take off at higher speeds typically, not planning it that way but the time to get from 60 to 80 is just a few seconds, and usually during my engine gauge check for final takeoff decision usually I’m beyond my rotate speed. Pull up, gain speed in ground effect, then gain altitude and gear up. Flaps up at safe altitude. I’ll try the rotate at 60 to ground effect to see if I can get her off the ground, I usually find that I cannot get her off the ground and I don’t want to yank the yoke, so I just wait the 2 seconds to gain more airspeed to rotate. Tires are rated well beyond 100mph so I’m not worried about that.
 
I trained in a PA-180, too. If you start lifting the nose at 60, with a smooth pull, you're at 75-80 by the time you're fully airborne. It will stay on the runway until 80, sure, but I'm not sure why your CFI would want that.
 
I like the airplane off the ground as soon as it will fly. Coming back to flying on my first few takeoffs, the airplane would become skitterish, nose wheel might vibrate, airplane would start lifting on it's own, what ever. That was the airplane ready to fly and me waiting for a certain speed. When it's ready to go, gently lift the nose and fly. Full power holding the airplane on the ground waiting for a speed that is too fast will eventually lead to bad things happening IMO.
 
Shouldn’t be a problem in ground effect. Accelerate to Vy or more before climbing out.
 
Jim K said:
You'll get a feel for it. A cherokee takes a good firm pull to get off the ground at the book rotation speed, and you'll stall it if you don't reduce that back pressure once she's off the ground. I've become a fan of the firm pull to break the ground and let her accelerate in ground effect. Significantly shorter ground roll, and I feel like you get to Vy faster. It's hard to convince yourself it's okay to pull that hard at first.

Second fastest is to let her accelerate on the ground and basically fly off on her own like your cfi suggests. I feel like the plane gets squirrelly and hard to control at higher speeds though, and with cherokees your front wheel is connected to your rudder, which exacerbates this issue in a crosswind.

The worst of both worlds IMO is doing a light pull and pulling the nose off and wheelying down the runway. That solves the nosewheel steering issue, but the induced drag slows your acceleration and increases ground roll significantly.
Click to expand...

Thanks, makes sense.

kgruber said:
You don't "rotate" a Cherokee.

You only "rotate" a swept-wing jet.
Click to expand...

Please forgive me.
FAA Handbook: "Vr- Rotation Speed. The speed that the pilot begins rotating the aircraft prior to liftoff."
 
tobnpr said:
Please forgive me.
FAA Handbook: "Vr- Rotation Speed. The speed that the pilot begins rotating the aircraft prior to liftoff."
Click to expand...

Which is the correct description. I think your instructor seems to believe that the airplane will break ground at Vr, hence the recommendation to wait for a faster speed to “rotate”. You don’t yank it off the ground at Vr, you just lift the nose at Vr and as the airplane continues to accelerate it will eventually fly.
 
tobnpr said:
Please forgive me.
FAA Handbook: "Vr- Rotation Speed. The speed that the pilot begins rotating the aircraft prior to liftoff."
Click to expand...

You are forgiven.

It is a common misconception. Note that the FAA says "begins rotating the aircraft."

Yes, you do rotate some airplanes like the swept-wing Lear Jet and Falcon 50 I am typed in. But that statement doesn't say ALL aircraft are rotated.

In light aircraft like the Cherokee, which I have thousands of hours instructing in, the nose wheel is unloaded and the airplane gradually lifts off.

 
Last edited:
With many planes like the PA28 you should be able to feel when she wants to fly and ease/let her fly off

Energy is your friend
 
There seems to be two approaches noted in the comments. Those who consider the possibility of LOTOT for every takeoff. And those who don't. Ok, maybe three if you include those flying jets.

For those who place a priority of LOTOT, you clearly want to get off the ground as soon as possible, which involves "rotating" (FAA definition) at the POH recommended speed, in most cases. I'm definitely in this camp.

I know there are a few planes where "letting it fly itself off" are essentially the POH recommended technique. However, for the majority of our GA aircraft rotating at POH recommended speed will give you more altitude, in a shorter time, should you have a LOTOT. Why this would not be the most critical factor in this discussion is beyond me.

I get that many CFI's seem to be getting more and more conservative as time goes on. But some if these seemingly "conservative" approaches (higher takeoff speeds, higher approach speeds) actually put the pilot and plane at greater risk. Learn your book numbers, understand aerodynamics, understand the fundamentals of aircraft control, and fly your aircraft based on facts and understanding, not on "some recommendation from a CFI".
 
I have a pet peeve about people using uncommon acronyms without at least once specifying the meaning. It’s a particularly common practice in my field and it annoys me to no end.
 
Salty said:
I have a pet peeve about people using uncommon acronyms without at least once specifying the meaning. It’s a particularly common practice in my field and it annoys me to no end.
Click to expand...
Yup....what the heck did he just say. :eek:

and most of us here have some credentials and experience.....but when I win the LOTOTTO....I'm goin fly'n. :D
 
Last edited:
Salty said:
I have a pet peeve about people using uncommon acronyms without at least once specifying the meaning. It’s a particularly common practice in my field and it annoys me to no end.
Click to expand...

LOTOT= Loss Of Thrust On Takeoff.

My peeve is using airport identifiers without the associated name and city...
 
My philosophy is to have fun without getting kilt. Almost every takeoff without inexperienced nervous passengers or gusty winds is a soft-field takeoff. It’s just more fun to come off the ground, accelerate, and then climb. More relaxing too. Something about a long ground roll just makes it feel unnatural in a seat-of-the-pants “I am one with the machine” sort of way. I know that’s weird.
 
Though it’s unlikely I’ll ever get to fly a 747, but about 2:20 into the video below reflects my mental imagery of what a proper rotation looks like:

 
eman1200 said:
there is a strategically placed bump in the runway at my home field where if I’m solo and trimmed perfectly the plane will conveniently be placed into a nice climb without me doing a damn thing
Click to expand...
At my home drome, there's a number of strategically placed bumps to help regardless of weight or plane or runway I might be flying.
 
Racerx said:
At my home drome, there's a number of strategically placed bumps to help regardless of weight or plane or runway I might be flying.
Click to expand...
Does the grass in the runway extend the height of the ground effect in your experience?
 
Jim K said:
Does the grass in the runway extend the height of the ground effect in your experience?
Click to expand...
The opposite. Pulls it to terra firma pretty quick when the grass starts hitting the leading edge. She ain't the greatest airport, but it's 10 minutes from home. And I feel like if I can land there safely I can land anywhere. Currently for sale and would love to get a group together to buy it. Instead of leasing the hangar you'd own it type thing.
 
Last edited:
noahfong said:
^^^^ Agree with this.
I'm noticing that many newer flight instructors want to see faster speeds than specified in the POHs. Not just for rotation, but for approach as well. Not sure what's going on but am believing they've become wimps of some sort. Anyone else noticing this? Any insight?
Click to expand...
Yup. Seen that a lot. Fear of the stall does it. They need to get some stall/spin training, lots of it. They need to go up to altitude, set the power and flaps for approach, for example, then start raising the nose and watching the ASI to see what it says when the stall break happens. That gives them an idea how far above the stall they are when using book speeds for approach. Do the same thing for climb, flaps up, full power, see what the ASI says when it stalls.

Too much speed wrecks a lot of airplanes. On takeoff, the Cessna nosegear takes a real pounding from imbalanced nosewheels. That costs money, causes shimmy, wrecks stuff. On landing, pilots end up porpoising, or ballooning and landing real hard, or running off the end, wheelbarrowing to wherever the airplane feels like going, or skidding tires that blow out when the pilot tries to fix the problem with brakes when the excessive airspeed means the wing is still taking most of the weight. Just because the wheels are on the ground does not mean that all the airplane's weight is on them. The flight is not over.
 
I generally agree with "rotating" at POH recommended speeds. One exception, IMO, is high density altitude, where the reserve power needed to climb is less. Then, I like to be closer to Vx to ensure I have the ability to climb out of ground effect.
 
If I'm barreling down the runway in my PA28R at 80 mph and haven't at least applied back pressure to get the nosewheel off the ground, I'd just assume I've decided to drive my Arrow to my destination instead of flying.

I strongly suspect the CFIs instructions are correlated with this being your first preflight briefing (presumably your first flight?). I imagine they do not want you to overenthusiastically apply back pressure at 60 only to end up skipping along the runway.
 
Tom Wells said:
I strongly suspect the CFIs instructions are correlated with this being your first preflight briefing (presumably your first flight?). I imagine they do not want you to overenthusiastically apply back pressure at 60 only to end up skipping along the runway.
Click to expand...
Bad, bad teaching. He's harming the student. From the Canadian Flight Instructor Guide:

upload_2023-1-8_13-54-15.png

Some detail:

upload_2023-1-8_13-55-30.png

So guess what that instructor learned on his first flights? The wrong stuff, and he's passing it on.
 
I suspect the higher rotation speed is, like many techniques, a corruption of some technique that was used as a training aid…your instructor had you fly all the way down final in a slip to learn the sight picture and control inputs for a crosswind landing, so now it’s the required procedure for landing with wing low into the wind. Your instructor had you fly 10 knots faster for wheel landings so you’d have a little extra time to find the ground with minimal sink rate, so now wheel landings require extra speed. Your instructor had you delay rotation in gusty crosswinds so you didn’t skip sideways on the runway before you were firmly airborne, so now it’s better to delay rotation.
 
Dan Thomas said:
Bad, bad teaching. He's harming the student. From the Canadian Flight Instructor Guide:

View attachment 113798

Some detail:

View attachment 113799

So guess what that instructor learned on his first flights? The wrong stuff, and he's passing it on.
Click to expand...
Oh for sure, totally agree.
IDK for sure that's why he's doing it, I just can't think of a reason why else you would overshoot the speed so much? :dunno:
The only thing that stands about the OP's situation is that it was their first flight...
 
Last edited:
You must log in or register to reply here.
Back
Top