View Full Version : True or false - balance

7th Oct 2016, 23:58
If I tell my students the following, is it true, or not the whole story?

"If I am flying straight with wings level, I am in balance".

8th Oct 2016, 09:09
Accel'ing or not? Only truly "in balance", if T=D, W=L, etc etc.

8th Oct 2016, 10:49
How much control deflection is required to stay straight and level?

Genghis the Engineer
8th Oct 2016, 19:05
Not the whole story.


8th Oct 2016, 22:40
Would it be better if I said,
"I am flying with a constant heading, constant speed and wings level, I am in balance".

Genghis the Engineer
8th Oct 2016, 23:16
How about, "the ball is in the middle therefore I am in balance" ?

Do they not cover the basics of S&C on professional pilot courses dunnunda?


9th Oct 2016, 00:35
Let me put it another way:

"If we are attempting to fly Straight and Level, and the ball is not centered, what could be the reason?"

9th Oct 2016, 10:53
"If we are attempting to fly Straight and Level, and the ball is not centered, what could be the reason?"

Not sat in the seat correctly? :}

9th Oct 2016, 11:21
Perhaps my initial question required a greater introduction.

During my own training I was adamantly told that straight and level flight means:
(five criteria)
wings are level,
constant height,
constant heading,
constant airspeed, AND
ball is in the center.

However, I always maintained that if the aircraft is ACTUALLY flying with wings level and at a constant height and heading, it would be balanced by definition. That is, if the ball is not centered in straight and level flight, one of the first four criteria is not being met. I'm not even sure airspeed is strictly a consideration in S&L flight.

Is the classroom definition of S&L flight most simply:
Constant heading, constant altitude, and in balance.

9th Oct 2016, 15:20
I'm not even sure airspeed is strictly a consideration in S&L flight.

Certainly is in S&L(2) !

9th Oct 2016, 20:23
Ok so when we say S&L means constant heading, height, airspeed, wings level, and in balance, does 'in balance' refer to the four forces being equal (and the aircraft is in equilibrium), or are we referring to the balance ball being centered?

9th Oct 2016, 21:24
What is Balance??
Balance ball to the middle.
Why not say it this way- Power + Attitude = Performance (in your case S&L)
Power; controls the speed
Attitude; Pitch for height, wings level for DI, and Rudder for ball...no sideslip
confirm it with instruments IAS, ALT, DI, TC
Performance; S&L at say whatever speed you want.
And trim

hugh flung_dung
9th Oct 2016, 22:02
rub... I see from earlier appends that you're either training for or preparing for your FI rating. During S&L training it's important to get the stude to understand that gross imbalance can be seen and corrected by looking over the nose but that small amounts of imbalance can not be easily recognised. If the aircraft is out of balance (i.e. flying slightly sideways) it is inefficient so therefore the balance ball needs to be used to detect and correct small amounts of imbalance. Corrections to balance should be made while looking over the nose rather than while staring at the ball.
... but all this will be covered by your FI instructor and will be in whatever book you choose to buy to help with briefings and patter.

Here's an extract from a (the?) bible:
"Indications of Straight and Level. Set the aircraft up straight and level, in trim with cruise power set. Briefly relax your grip on the controls to point out the stability - ie the attitude does not change. Teach the; indications of straight and level. These are:
a. Straight Flight. The wings are level - the coaming is parallel with the horizon . Point out that the wingtips are equidistant below the horizon. Use a reference point ahead to show that the aircraft is not turning or yawing,and is therefore in straight flight. This can be seen visually, and is confirmed by the DI showing a constant heading.
b. Level Flight.The instruments are needed to confirm level flight, as shown on the altimeter and VSI. The ASI shows a constant airspeed.
c. Attitude.Point out the visual attitude for straight and level flight at this airspeed and power setting. It is the datum attitude previously used in effects of controls.

Achieving Straight and Level Flight.
a. Straight Flight. Disturb the aircraft from wings level, and teach the student how to regain straight flight. Roll the wings level. Select a reference point ahead and stop any yaw with rudder. Trim the rudder.
b. Level Flight. Disturb the pitch attitude and teach the student how to regain level flight. Select, hold and trim the pitch attitude for level flight. Check the altimeter, adjust the pitch attitude and re-trim. Ensure that a small attitude adjustment is required after the first attitude selected, to show the student how to correct. Make sure the speed is I00 kts as the attitude for level flight is achieved. This is done by raising the nose and allowing the speed to fall to about 80 kts, and then selecting a nose low attitude and giving control to the student to select level flight. By the time he has selected the attitude, the speed will have increased to about 100 kts. To set the aircraft up in a nose high attitude first lower the nose and increase speed to about 120 kts, and then select a nose high attitude before giving control to the student. Ensure the power is left set for 100 kts, but that the trim is slightly mis-set.
c. Straight and Level. Disturb the aircraft from both straight and level flight, and teach the student how to regain straight and level. Roll the wings level. Select and hold the pitch attitude for level flight and stop any yaw visually. Trim the elevators and rudder - heaviest load first. Check the altimeter, and adjust attitude and re-trim if required.

Imbalance. Set the aircraft up in straight and level flight at cruising speed. and point out the speed. Make sure that the fuel is selected to both,and that the booster pump is on. Now cross the controls to achieve straight and ievel, but grossly out of balance. Point out that it looks wrong, the sideslip feels wrong, the reducing airspeed
<> how inefficient flight due to increased drag, and the slip ball is well out to one side. Gross imbalance is easy to detect. Reduce the rudder deflection , but still maintain a slight degree of imbalance. Point out that it looks and feels correct, but that the airspeed is still slightly reduced, and the slip ball is still out to one side. Slight imbalance is more difficult to detect, and the slip ball must be used. Teach how to regain balanced flight. Use rudder to
centralise the slip ball, trim the rudder, and then use ailerons to prevent any turn. Point out that if there is a clear horizon it is easy to level the wings accurately, and centre the slip ball, thus achieving accurate balanced flight. However, if the perceived horizon is sloping, the aircraft may be inadvertently flown out of balance by levelling the wings on the sloping horizon, and then preventing any yaw with rudder. Under these conditions it is essential to check the slip ball."

Here's the patter sequence:
1. Note speed in balanced flight. Make sure
the fuel is set to both, and the booster pump is on.
Cross the controls to demonstrate gross imbalance
in straight and level flight.
a. Looks wrong.
b. Sideslip feels wrong.
c. IAS reducing - inefficient.
d. Slip ball well out
2. Reduce rudder deflection to demonstrate slight imbalance in straight and level flight.
a. Looks correct.
b. Feels correct.
c. IAS still reduced - inefficient.
d. Slip ball still out.
e. Slip ball must be used to detect slight imbalance.
3. Teach how to correct to balanced flight.
a. Use rudder to centralize the slip ball.
b. Trim the rudder.
c. Use ailerons to stop any turn.
d. Use this technique to balance the aircraft.

This was OCR'd from a PDF so I apologise if any errors have snuck under the radar.


Capt Pit Bull
10th Oct 2016, 01:30
Balance requires:

Velocity vector perpendicular to lateral axis.

end of.