Bank Angle In The Circuit

[Big Pistons Forever]

He is saying that given a choice between A) and B) you should pick B). That is 100% true, easily demonstrated and therefore perfectly correct advice. Naturally a well planned 30 degrees or so is preferable and won't scare your passangers but putting that rudder in to speed up the turn and keep the bank angle below 30 is dangerous and if you are intent on speeding up the turn for whatever reason increase the bank angle and stay co-ordinated instead.

Exactly

[ross1]

"I am turning downwind with 130 (no typo) degrees of bank. My
accelerometer is indicating precisely +1.0 G and the ball is in
the center. What is my stall speed?

Bonus question: if I stall, which way will the aircraft go?"

...seems to me that 1G is 1G in any attitude....stall speed remains the same (Vs X sqroot G)...nose will momentarily move towards you feet til that 1G quickly becomes 0, then the airplane falls towards the ground..??

[old_man]

Alright, woke up this morn and thought more about it. No 1G is not 1G in any attitude. If you are inverted you have to pull a lot to get 1G on the meter. Gravity only works in one way.

So I did the math and I came up with a total load factor of 2.55 which increases stall speed by 60%.

Am I close?

[DanWEC]

I'll take a stab at your response oldman....
By virtue of coming up with an increased load factor, you wouldn't be pulling 1g, so that's inherantly incorrect.
With 1g and ball centered, you're in a condition where all forces, whether counteracting gravity or in association with it, currently acting on the plane are resulting in the exact same condition as if it's flying straight and level, no matter what.

So those forces are resulting in force pushing towards the floor of the airplane of 1g. The wing is lifting in the opposite direction, towards the roof of the the plane.... and only having to counteract a 1g pull... Therefore just like its straight and level, therefore a load factor of 1 and standard Vs.

The video of the the airliner doing a barrel roll while maintaining 1g the entire time comes to mind.

Hope I'm right, otherwise I just sound like a tool.

[ross1]

...watch Bob Hoover pour a glass of tea.

[Grantmac]

I probably CAN'T comment because I'm a lowly PPL with about 230ish hours to my name. However half of that has been in a fabric taildragger without flaps. That probably gives me even less credibility because of the lack of complexity of the aircraft.

Slips and slipping turns are a reality, not just some exercise to be performed upon request. In this particular aircraft a full slip requires around 30 degress of bank, I saw around because there is no AI. A slipping turn is substantially higher bank to achieve much change of direction. I am more than happy to do them onto final and then hold that 30 degree bank in full slip right down to the fence.

I'm not sure why everyone is afraid of the big, bad stall in a turn. I've always thought it was the least dangerous. Reduce the load factor a little, lose a tiny bit of altitude, roll level and its over without being an event. Perhaps time spent attempting to core thermals was well spent for something other than padding my logbook?

-Grant

[iflyforpie]

Slipping is fine, it is skidding (using bottom rudder) that is dangerous.

[CpnCrunch]

Ok, so perhaps the aerobatic pilots could explain the cirrus crash. What seemed to happen was:

- pilot did a level 60-degree bank turn to the left
- the entire left wing (including aileron) stalled, resulting in a yaw to the left and incipient spin
- pilot (naturally) corrected with right (top) rudder, which resulted in an unrecoverable snap-roll

[erics2b]

I am turning downwind with 130 (no typo) degrees of bank. My
accelerometer is indicating precisely +1.0 G and the ball is in
the center. What is my stall speed?

Bonus question: if I stall, which way will the aircraft go?

Are you asking which direction will the (vertical component of the) aircraft's velocity be directed? Or acceleration? Or change in acceleration? You can interpret that in any of the above ways, and they don't all have the same answer!

[Colonel Sanders]

Hi Eric. The point of the question was to challenge
people's acceptance as fact that a stall always results
in the nose dropping back to the ground. Gravity has
overcome lift.

However, consider the case where an aircraft is inverted wings
level - forget about any bank, that's simply me being cruel
as usual - approaching the top of a very high speed inside loop,
and then attempting to pull (e.g.) +6G's. If the aircraft doesn't
have enough airspeed, it will stall.

When the aircraft stalls, it will fall upwards which I am
sure will make people here howl - they will say it's impossible
to stall, and fall upwards.

Sure you can.

The forces acting on the aircraft are simple vector summation.

We have one lowly G downwards (gravity) but a crapload of
centrigual force pulling the aircraft upwards, which is opposed
by the lift of the wings pulling the aircraft downwards. Gravity
and lift pull the aircraft down.

If the lift of the wings disappears - consider it to go to zero,
which of course it won't - then all you have left is the ballistic
summation of the +1G of gravity and the upwards centrifugal
force, which overcomes the +1G of gravity, and the aircraft
falls upwards when it stalls.

I tried to drop a hint when I posted the picture of the water
bomber releasing water while pulling G inverted - note that
the released water, like a stalled aircraft, falls upwards - but
I guess that didn't help.

Doing outside loops, many many times I have stalled and
fallen upwards. Start inverted, straight and level, and push.
If you don't have enough entry speed (or G) as the aircraft
falls through the vertical - it is now in an upright 45 upline,
but with fading negative G on, trying to push the nose down -
the aircraft with tremble and grumble with a negative AOA
stall. If it happens, you fall upwards as centrifugal force
overcomes combined lift and gravity.

Actually, what I like to do right then, is say ok you mother,
let's do it - full forward stick and full rudder to asymmetrically
negative G stall, which gives you the prettiest little half outside
snap roll. You end up inverted (instead of upright) at the top
of the loop. Pulling through is not recommended because of
GLOC considerations, though. Pity.

tl;dr You can have a positive G stall which results in the
aircraft falling upwards



Last time I checked, a waterbomber wasn't usually
considered eligible for aerobatic competition, so I
really haven't rigged the deck that badly.

Bonus question: talk to me about the energy of
the water in the above photograph. There is a
fascinating lesson there, if you notice a little detail.

[126.7_STFU]

No airshow video to go along with that explanation???

[TC Aviator]

Thanks Colonel Sanders, wise advice for the training folks and those that are shy of anything greater than a shallow banked turn.

[cgzro]

yes your stall speed at 1g is vs no matte the orientation. The stall inverted and turning will reduce the lift available to turn you and reduce the lift available to pull you toward the groung.
So the end result is more correctly described as a reduction in the rate of turn and reduction of rate of descent. The coordination means no roll change.
That could give a brief falling up:)

One of my fav manoruvers is the avalanche which is a horizontal spin from inverted at the top if a loop. As you stall into the spin the loop radius decreases temporarily until you recover and the lift is back pulling you downward again. In essense you fall up (or less down) briefly.

Ill post a rear facing vid in next post.

[ross1]

[quote="ross1"...nose will momentarily move towards your feet til that 1G quickly becomes 0, then the airplane falls towards the ground..??[/quote]

I assume that the center of pressure still moves backwards at the stall and causes the "nose down" (upward) rotation on the lateral axis?

[quote=
Bonus question: talk to me about the energy of
the water in the above photograph. There is a
fascinating lesson there, if you notice a little detail.[/quote]

It still travels in a straight line...

happy flying!
RB

[looproll]

60 degrees of bank is great for getting the top and bottom wing out of the way for a look

I like the bold block in the theory of flight section of the "From The Ground Up"

an aircraft will stall at any airspeed if the critical angle of attack is exceeded
an aircraft will stall at any power setting if the critical angle of attack is exceeded
an aircraft will stall at any attitude if the critical angle of attack is exceeded

I flew with a low time pilot not long ago and it was the worst example of skidding I have ever seen. He was glued to the turn coordinator when making a turn in the circuit. I urged him to get his eyes outside and see and feel what the airplane is doing.

[frog]

How could you skid with the eyes glued to the TC ?

[Shiny Side Up]

How could you skid with the eyes glued to the TC ?

Usually because if you're so enthralled by the instruments you're probably reacting to the aircraft rather than anticipating it. It doesn't take a rocket scientist to anticipate the yawing tendancies of the airplane and control them rather than correct them. Ounces of prevention, pounds of cure and all that.

[Colonel Sanders]

I urged him to get his eyes outside and see and feel what the airplane is doing

When you get relaxed in an aircraft, your muscles are not all tensed up. And when the ball is not in the center, your bottom is tied to the seat via the seatbelt but your shoulders move back and forth. This is an unpleasant feeling in your lower back.

However, students are not relaxed in the aircraft. They are working very, very hard and are all tensed up. They cannot feel their shoulders moving back and forth, because their muscles are all so tight.

Sitting in the right seat of an aircraft, looking out the window, I can tell people what rudder they need to use, by the feel of my shoulders moving back and forth. If my right shoulder is pinned to the door, they need to use some right rudder. I don't need to look at the ball. Neither does anyone else, really, modulo illusions created by drift (the orphan lesson).

A circuit is a visual, not an instrument exercise - at least, during the day!

[Shiny Side Up]

Sitting in the right seat of an aircraft, looking out the window, I can tell people what rudder they need to use, by the feel of my shoulders moving back and forth.

I'm usually wedged into the airplane to tight for that so I rely on the feeling of weight transfer between my butt cheeks. Sometimes there's problems like this though.

[Geo]

Bonus question: talk to me about the energy of
the water in the above photograph. There is a
fascinating lesson there, if you notice a little detail.

Hmm. I see water falling upwards, and some starting to disperse and fall down. I'm going to go with:
Kinetic Energy being converted to Potential Energy in the short term, with a return to Kinetic after a brief pause.

In short, the water "is going ballistic Mav!"

What I find interesting in the photo is the dispersed trajectory of the water streams as they are released continuously along the arc the plane is following...but oh HEY! The water all peaks along a horizontal line (plus or minus a bit)...so the total energy (KE+PE) of the of the bomber is plotted by the top edge of the arc of the water in the sky? Or am I reading too much into that?

g

[Colonel Sanders]

The water all peaks along a horizontal line

Regardless of where the water was released, it has equivalent
energy which is defined as kinetic energy plus potential energy.

[iflyforpie]

The water all peaks along a horizontal line

Regardless of where the water was released, it has equivalent
energy which is defined as kinetic energy plus potential energy.

Not quite. The engines are still adding energy to the water released later. Now, if Manfred Radius decided to release some water ballast in a loop....

[Big Pistons Forever]

Let see the title of this thread is "Bank angle in the circuit" and we are now talking about the physics behind an inverted water drop

Thread drift sure can be entertaining, not to mention enlightening in many weird, wonderful and unexpected ways

However at the risk of being a killjoy and actually returning to the topic at hand, IMO a "good" circuit during PPL training is one where co-ordinated turns using not more than 30 degrees of bank are used. If you have to use more then 30 degrees of bank, particularly on the base to final turn, you have misjudged the turn and should work at recognizing how that misjudgment occurred ( ie late turn, not accounting for wind, not keeping a constant bank angle etc) not just crank on more bank even if it is perfectly co-ordinated.

If you have passengers you may be perfectly happy at high bank angles but your passengers probably won't. In any case cranking and banking often isn't the sign of a good pilot, just an aggressive one. When the really great ones fly they are so smooth nothing seems to happen yet almost magically the aircraft is always in the perfect spot for what ever is coming up next in the flight.

[Colonel Sanders]

The engines are still adding energy

Close. Only the excess thrust (after parasite
and induced drag is deducted from total thrust) is
being added.

This is why it is so important to keep the G down.

Young guys like to impress everyone with the incredible
G they pull. However, when you pull all that G, you
are operating at a very high alpha, and the Cd curve
is exponential wrt AOA!

The better a pilot someone is, the less G they need
to pull to fly a given maneuver. Allows them to
conserve energy.

An extreme case of "Young Guy Pulls Too Much G"
is the famous "cobra" maneuver, which ends up
with the aircraft stopped in the sky. It is supposed
to be a heroic maneuver to position you on the tail
of another aircraft, but if there's a third aircraft in
the sky that doesn't like you, it's his birthday.

[Colonel Sanders]

back on topic ....

If you have to use more then 30 degrees of bank,
particularly on the base to final turn, you have misjudged
the turn

For sure. What I don't like is when someone is in that
situation, and rather than using bank to turn the aircraft,
they stomp on the inside rudder to haul the nose around.

This makes me jibber like a chimpanzee with Tourette's
Syndrome as I try to explain why that is a very bad thing
to do.

Instead, what I suggest to people is that they turn the
aircraft with bank instead of yaw. A slight momentary
increase in the bank - remember, the G is light in the
descending turn, and thus the stall speed is reduced
below the +1G Vs - and the ball falls back to the center,
and the aircraft turns in a co-ordinated fashion.

Much less dangerous than a flat turn with rudder.