Cessna 172....Pitches for Vx and Vy

On Mar 28, 2:16 pm, Sushidot <sushi...@> wrote:
> Hi-
>
> Just wanted to know generally what pitch on takeoff I should expect,
> generally, for Vx and Vy, on the AI?
> Thanks
> SD

The pitch won't be extreme. I don't teach students to climb based on
pitch because the pitch you choose is too dependant on current
conditions. Pitch for airspeed. Too many pilots don't make it off the
runway at high density altitude simply because they try to ask the
plane for a pitch it can't do.

-Robert, CFII

On Mar 28, 4:20 pm, "Barry" <a...@b.c> wrote:
> > I don't teach students to climb based on
> > pitch because the pitch you choose is too dependant on current
> > conditions. Pitch for airspeed. Too many pilots don't make it off the
> > runway at high density altitude simply because they try to ask the
> > plane for a pitch it can't do.
>
> Here's another opinion.  I teach that the pitch should always be set to some
> desired attitude (using position of the nose if flying visually, or the
> attitude indicator if on instruments) and that the airspeed indicator should
> serve only to confirm the desired performance.  I find that pilots who set
> pitch using the airspeed tend to have more trouble flying smoothly.  This is
> especially evident just after takeoff (pitch attitude oscillates as the pilot
> chases the airspeed, which takes a few seconds to stabilize).  Note also that
> airspeed indicators can give faulty readings (water inside the pitot, for
> example) and I think that this poses an additional risk for pilots who rely
> heavily on airspeed for pitch control.
>
> I'd like to hear from other instructors on this issue.

I don't necessarily disagree with you. However, I teach at the foot of
the Sierra Nevada mountains. My number one concern with regard to
pitch is that students can handle a variety of density altitudes. I'm
willing to make things a bit harder for them in return for them
understanding that its IAS that makes the plane climb.

-Robert

On Mar 28, 5:16 pm, Sushidot <sushi...@> wrote:
> Hi-
>
> Just wanted to know generally what pitch on takeoff I should expect,
> generally, for Vx and Vy, on the AI?
> Thanks
> SD

That would greatly vary with density altitude. Even at a fixed
altitude, AI is not going to give you accurate pitch information for
Vx and Vy. What's wrong with using the ASI?

On Mar 29, 12:20 pm, "Barry" <a...@b.c> wrote:
> > I don't teach students to climb based on
> > pitch because the pitch you choose is too dependant on current
> > conditions. Pitch for airspeed. Too many pilots don't make it off the
> > runway at high density altitude simply because they try to ask the
> > plane for a pitch it can't do.
>
> Here's another opinion.  I teach that the pitch should always be set to some
> desired attitude (using position of the nose if flying visually, or the
> attitude indicator if on instruments) and that the airspeed indicator should
> serve only to confirm the desired performance.  I find that pilots who set
> pitch using the airspeed tend to have more trouble flying smoothly.  This is
> especially evident just after takeoff (pitch attitude oscillates as the pilot
> chases the airspeed, which takes a few seconds to stabilize).  Note also that
> airspeed indicators can give faulty readings (water inside the pitot, for
> example) and I think that this poses an additional risk for pilots who rely
> heavily on airspeed for pitch control.
>
> I'd like to hear from other instructors on this issue.

I'm not an instructor but the idea of reaching Vx by reference to AI
sounds potentially dangerous to me. Surely, the AI is no proxy for AOA
and that is the most important factor at take off.

Cheers

On Mar 29, 12:27 pm, "Robert M. Gary" <N70...@> wrote:
. I'm
> willing to make things a bit harder for them in return for them
> understanding that its IAS that makes the plane climb.
>


\Why is that so hard to undertsand/teach? Steady climb is only a
function of spare thrust (i.e. trust beyond that needed to overcome
drag)....

Cheers

On Mar 31, 1:49 am, Dudley Henriques <dhenriq...@rcn.com> wrote:

>
> I like pilots to KNOW the numbers for the aircraft/density altitude
> equation that will be present on their intended takeoffs and fly those
> numbers.
> On high density altitude takeoffs, the pilot should be looking for the
> predetermined indicated airspeed needed for Vx or Vy peripherally  as
> with any other takeoff.

The only numbers I can think of are are take off and landing distances
(maybe static RPM too). (ASI Vx and Vy don't change) but what other
numbers should I know?

Cheers

WingFlaps wrote:
> On Mar 31, 1:49 am, Dudley Henriques <dhenriq...@rcn.com> wrote:
>
>> I like pilots to KNOW the numbers for the aircraft/density altitude
>> equation that will be present on their intended takeoffs and fly those
>> numbers.
>> On high density altitude takeoffs, the pilot should be looking for the
>> predetermined indicated airspeed needed for Vx or Vy peripherally as
>> with any other takeoff.
>
> The only numbers I can think of are are take off and landing distances
> (maybe static RPM too). (ASI Vx and Vy don't change) but what other
> numbers should I know?
>
> Cheers

Well, you want all the numbers for the takeoff that influence the
density altitude calculations for that specific takeoff at that exact
time and temperature.
Also, recheck your assumption that Vx and Vy IAS doesn't change with
altitude. There are in fact IAS changes in both these figures with
altitude increase.
IAS for Vx increases slightly with altitude and IAS for Vy decreases
with altitude. They will meet at the same point which should be the
absolute ceiling for the aircraft.

--
Dudley Henriques

On Mar 31, 10:52 am, Dudley Henriques <dhenriq...@rcn.com> wrote:
> WingFlaps wrote:
> > On Mar 31, 1:49 am, Dudley Henriques <dhenriq...@rcn.com> wrote:
>
> >> I like pilots to KNOW the numbers for the aircraft/density altitude
> >> equation that will be present on their intended takeoffs and fly those
> >> numbers.
> >> On high density altitude takeoffs, the pilot should be looking for the
> >> predetermined indicated airspeed needed for Vx or Vy peripherally  as
> >> with any other takeoff.
>
> > The only numbers I can think of are are take off and landing distances
> > (maybe static RPM too). (ASI Vx and Vy don't change) but what other
> > numbers should I know?
>
> > Cheers
>
> Well, you want all the numbers for the takeoff that influence the
> density altitude calculations for that specific takeoff at that exact
> time and temperature.
> Also, recheck your assumption that Vx and Vy IAS doesn't change with
> altitude. There are in fact IAS changes in both these figures with
> altitude increase.

Interesting. Not listed in my POH, where can I find them? My
assumption about Vx and Vy was based on the idea that the Pitot
measures kinetic energy in the air stream and hence lift
availability... This not one of those funny compressibility things
that you jet jockies get to see is it?

Cheers