52 votes
Accepted

Why is this airplane flying in circles randomly?

What you observed is probably a Gulfstream production test flight, either an initial or a snag clearance flight, or possibly a Customer Acceptance from Savannah Air Center, which is a completion ...
user avatar
  • 107k
38 votes
Accepted

Can a plane bank without turning?

Yes it can. The steady-heading sideslip (SHSS) maneuver is used in flight testing to demonstrate static lateral/directional stability (similar maneuvers exist as sideslip approach in crosswind, or ...
user avatar
  • 10.8k
25 votes

Why is this airplane flying in circles randomly?

The fact that it's near Savannah and tracking within a confined airspace, I'm fairly certain this is a flight test being carried out by Gulfstream.
user avatar
  • 10.8k
25 votes

What does it mean when an aircraft is statically stable but dynamically unstable?

Static stability means that a deviation from a trimmed state produces forces which return the system to this trimmed state. If these forces produce an overshoot which increases over time, such that ...
user avatar
24 votes

Can gliding your plane save fuel?

This approach of using an engine is called pulse and glide. It generally works because each engine has an optimal power setting at which it converts fuel into power most efficiently. If the most ...
user avatar
  • 11.6k
19 votes
Accepted

What does it mean when an aircraft is statically stable but dynamically unstable?

If an aircraft is statically stable, it will always return to equilibrium after a disturbance. But what happens after can either show instability or stability. This is where the dynamic stability ...
user avatar
  • 1,823
18 votes
Accepted

Do any airplane designs exist that don't involve a flight surface that provides downforce?

There are multiple configurations which are possible with tail or canard, which based on their locations and whether they produce lift or down-force, results in a stable or unstable aircraft (taking ...
user avatar
  • 98.7k
17 votes

Can a plane bank without turning?

Yes, it's entirely possible. You can use the rudder to oppose the turn induced by the roll, and thus fly straight. However, doing so means that your nose is pointed off at an angle from your direction ...
user avatar
17 votes

Can gliding your plane save fuel?

Here is one thing that WILL save fuel-- where possible-- such as when flying VFR. Note that this strategy only applies within the layer where thermal convection or orographic uplift are significant, ...
user avatar
  • 17.4k
15 votes

Is a trimmed flight not always an unstable system?

But assume, there comes a wind gust, and the angle of attack will increase. This causes the center of pressure to move forward in front of my gravity location. So the aircraft will become instable ...
user avatar
  • 17.4k
13 votes

Do any airplane designs exist that don't involve a flight surface that provides downforce?

Of course, just put the center of gravity back to its rear limit and fly slowly. Then all of them will produce positive lift on their tails. Stability is not produced by a downforce at the tail. The ...
user avatar
12 votes

Is a trimmed flight not always an unstable system?

I think you misunderstand how it works, and how you would respond to changes in wind. Increases in airspeed impact all flight surfaces, including the elevator, so a change in airspeed due to a gust ...
user avatar
  • 50.2k
11 votes

Do any airplane designs exist that don't involve a flight surface that provides downforce?

A tandem wing airplane has two sets of wings, each providing upward lift. One is near the front of the plane, one is near the back, and the center of gravity is between them. (source: nurflugel.com) ...
user avatar
  • 1,123
11 votes

What is causing these "corners" on this F-104 V-n diagram?

what is causing the "corners" that we see at the following points? Compressibility. Close to Mach 1 the lift curve slope increases according to the Prandtl-Glauert rule with the factor $\...
user avatar
10 votes
Accepted

What is the effect of thrust vectoring effect on the rate of turn?

The standard equation applies to any coordinated level turn (so that the G felt is "straight down" to an occupant of the aircraft, in an aircraft frame of reference). Matters not how it's ...
user avatar
  • 42k
9 votes
Accepted

Where is the 'zone of reversed commands...'?

This is commonly known as the Speed Stability, not to be confused with speed stability in the sense of static longitudinal stability. I think there's some common confusion with this phenomenon. The ...
user avatar
  • 10.8k
9 votes

What exactly happens when power is reduced in trimmed, straight and level flight?

This makes sense and is approximately what happens if you reduce thrust during trimmed straight and level flight. The aircraft will go though a series of damped oscillations, called 'phugoid' until it ...
user avatar
  • 75.2k
8 votes

How can L/D Max be both Best Glide speed and Max Range speed?

I'm going to answer with the caveat that I don't have as deep of an understanding of this as I would like, and someone smarter than me may be able to correct or expound on my response. Best Glide is a ...
user avatar
  • 370
8 votes

What is the effect of thrust vectoring effect on the rate of turn?

With thrust vectoring you no longer turn (as in: the wing creates the force that accelerates you in the desired direction) but you do post-stall maneuvering. Next, you need to distinguish between ...
user avatar
7 votes

Where is the 'zone of reversed commands...'?

Both are right in their own ways. First the basics: Power is thrust times speed and is constant over speed for variable-pitch propeller-powered piston aircraft. Therefore, propeller thrust is ...
user avatar
7 votes
Accepted

What exactly happens when power is reduced in trimmed, straight and level flight?

You are very perceptive to note that for a given angle-of-attack, a return to the exact airspeed that allowed level (horizontal) flight would indeed imply a return to level (horizontal) flight. But ...
user avatar
  • 17.4k
7 votes

Can a plane bank without turning?

Here are two questions back at you. Can a plane turn, with banking? Yes, of course it can, the normal way using the ailerons to tilt the airplane and thus change the angle of lift. You already know ...
user avatar
7 votes
Accepted

Why do airplanes start descending when we initiate a left turn?

This is because when you roll left (or right), the lift changes from pushing up to pushing up + left (or + right). This is what makes you turn. Since some of that lift is being used to the left (or ...
user avatar
7 votes

What causes the ball to not be centered in a slip/skid?

It is the same thing that makes you slide sideways in your seat going around a corner in your car. Or the same thing that would cause you to slide sideways the other way if you were driving straight ...
user avatar
  • 16.4k
7 votes

Is a trimmed flight not always an unstable system?

Don't overthink it too much. Simplify in your mind. Trim is used to pre-set hands-off angle of attack. Static stability forces will focus on regaining the trimmed angle of attack if the plane is ...
user avatar
  • 107k
6 votes

In simple mechanical stick linkages, is there crosstalk between the aileron and the elevator movement?

In simple mechanical stick linkages, is there crosstalk between the aileron and the elevator movement? In almost all cases, there is no intentional-- or discernable-- mechanical coupling between ...
user avatar
  • 17.4k
6 votes
Accepted

In simple mechanical stick linkages, is there crosstalk between the aileron and the elevator movement?

As drawn, that linkage would cause elevator movement if you moved the stick in a perfectly lateral direction. But when you roll into a turn, you normally apply a little up elevator anyway, and in ...
user avatar
  • 107k
6 votes

Why is this airplane flying in circles randomly?

I would second what John K said, it’s most likely a GAC factory flight test or demonstration flight. Also with the airplane identified as GLF6 and, most likely going be the call sign “Gulf Test six” ...
user avatar
6 votes

Can a plane bank without turning?

Can planes bank without turning Yes, a plane may fly in a banked attitude without turning. But when the plane is tilted to the left or right relative to Earth's surface and gravity, shouldn't it be &...
user avatar
  • 17.4k
6 votes

Why is the L/D ratio numerically equal to the glide ratio?

The sum of all work done on the airplane must be zero in a glide. That is, the work done by gravity must equal the work done by drag. Note also that lift equals the force of gravity in equilibrium ...
user avatar
  • 12.1k

Only top scored, non community-wiki answers of a minimum length are eligible