# How long does it take on average for a control surface to deflect by one degree?

I know this should vary quite a bit (because of aircraft size / use / build / actuation / control surface weight), but I was wondering if anyone here could ball-park some numbers on how long it would take a control surface (aileron/flap/vertical stabiliser) to deflect by one degree on average.

I am writing a small aircraft simulator, and would like to try and use realistic numbers if possible.

If these figures are too variable, I would love to know some ball-park figures for some example aircraft if possible.

• Is that a small simulator of aircraft, or a simulator of small aircraft? Or said differently, are you primarily interested in data for small aircraft? Certainly the Ikarus C42 will happily slam the flaps back to neutral if you aren't careful to hold the lever when releasing the lock. I wouldn't guess a duration, but it's a lot faster than you can react.
– user
Commented Nov 14, 2018 at 9:21
• In a cable driven system, the only "delay" is the "slack" in the cables, which there should be none, so you can assume they react as quickly as the movement on the control column/yoke. Commented Nov 14, 2018 at 15:10
• Yeah, what Ron said. Make it equal to the rate of control movement and call it good. Commented Nov 14, 2018 at 16:57
• ...except that, if it's a PC simulator which uses a typical joystick, it will still be much faster than real: a full travel can be done in 0.1 s or so on a PC joystick. Still, this will likely cause much smaller error than many other unavoidable assumptions.
– Zeus
Commented Nov 15, 2018 at 8:07
• It depends how fast you move the controls. Commented May 12, 2019 at 4:23

With hydraulically actuated flight controls, the deflection speed is only limited by the maximum hydraulic fluid flow through the servo valve. I've taken some step responses of civil airliners in the past, and on-ground they can deflect full range in about 1-2 seconds.

For a mid-range passenger jet:

• Elevator range = 42 deg, max no load deflection speed = 66 deg/sec
• Aileron range = 40 deg, max no load deflection speed = 66 deg/sec
• Rudder range = 48 deg, max no load deflection speed = 56 deg/sec

At higher airspeed the maximum deflection angle and speed become less due to aerodynamic blowback - by design, to limit the inertia forces on the airframe.

• I once saw this when technics tested elevator after replacing one of the ELACs on A320. It was mesmerizing to witness elevators make full deflections several times at maximum rate. I’d say it was less than a second from neutral position from to full deflection but definitely it was lot faster than normal speed when using sidestick. I’d say normal full deflection on the ground takes some 2-3 seconds. Commented May 12, 2019 at 7:39
• @busdriver Yes very powerful motion indeed. The data above is not from an A320, but from a comparable size jet with conventional mechanical cable type flying controls. The cited times are my projections, it takes some time for the control surface to be accelerated to maximum no-load deflection rate. Commented May 12, 2019 at 10:20

For a fighter jet, specifically the F-16 the max deflection speeds were:

Flaperons: 80 deg/sec

Rudder: 120 deg/sec

Horz.tail: 60 deg/sec

Note: The horz. tail value is from a Langley F16 simulator paper (TP-1538, you can find it on NASA technical document server), so might not reflect what it was on the physical plane, but it was 2 digits.

The source for the other 2 numbers is a flight control systems block diagram probably anno 1975. with a little googling you can probably find it on the Internet.