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Newbie Joined: Jun 11, 2004 Posts: 2 Status: Offline

Is anyone experienced in a Yaw Departure doing a maximum command roll? (23000' - 270 Knots). The pilot change 480 degrees when the Departure happened.

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What was the external stores configuration at the time?

Whew! A yaw departure!

Musta been exciting for a bit, then resetting all the FLCS caution lights because the sensors detected 'backwards' flight! He heh.

Hey! STBYGAIN and Cylon and Osprey-dude! Jump in here.

Only way I can see to 'depart' the Viper is to have external stores and high-AOA, then command full roll. A clean Viper, well one with only wingtip missiles, is prolly impossible to depart no matter what 'Joe Baggodonuts' does. The thing was built that way so we could yank and bank without fear of 'departing'.

With external stores and FLCS set for the loadout, it would still be difficult to depart, but not like in the A2A config. Of course, if you have just dropped a 2000 pounder from one side and roll into the heavy wing real hard I can see where the flaperons and rudder couldn't arrest the yaw.

This was a serious problem with the older jets, BTW. I speak from experience. A-7D was notorious for 'departures', and I tink the Double Ugly had some bad characteristics unless pilot locked stick between legs and used only rudder to roll.

let's see what other inputs and opinions and experiecne we get, huh?

Neat thread.

Newbie Joined: Jun 03, 2004 Posts: 13 Status: Offline

There's a very good article on departing the viper (or how not to) written by Joe Dryden. This is the link http://www.codeonemagazine.com/archives ... index.html

Young conversion pilots like me hope we never ever face a situation which results in departing the viper. So far I haven't done anything dumb enough to come even close. So far...

Enthusiast Joined: Feb 10, 2004 Posts: 72 Status: Offline

I know the USAF trains instructors in departure recoveries. One of my instructors did that training. I was just wondering if 'normal' viper pilots in the states have to do that training as well, anyone?
It's a bit sad that we don't train pilots to recover from a departure...we only do it in the sim sometimes but thas is hardly compared by the actual 'sensation' I guess. My knowledge about this stops by the books. If you don't rape 2 limiters at the same time you should remain out of troubles but I would like to know how it feels...

Enthusiast Joined: Jan 28, 2004 Posts: 47 Status: Offline

Quote:

Only way I can see to 'depart' the Viper is to have external stores and high-AOA, then command full roll.

Case in point... was in a classic side-by-side stack that I happened to be winning. The bandito bails out of the stack under me, so I roll to 90 deg left to gain sight when my fangs come out and I commit the 2 limiter sin of full aft stick and full left roll. The jet pitches up and to the RIGHT. It was a Blk-40 with a centerline tank which a lot of dudes feel is the most susceptible to departing. Not sure if there's any flight test data to prove it though. Either way, that's the last time I tried that stunt.

Burn

A problem was found during flight testing of the MCID big mouth intake, especially bad with centerline tank and high AoA at certain speeds/altitudes. The flight control software was modified as a result. Evidently the larger (wider) inlet upset airflow around the forebody strakes and wingroot at AoA. I have a copy of an old AvWeek article describing the problem in detail.

Newbie Joined: Sep 28, 2003 Posts: 8 Status: Offline

hi there, what do you mean by a departure?

Departure, Outta control flight. Spinning and flopping around in the air with no lift, nice way of saying Oh S***.

Newbie Joined: Jun 11, 2004 Posts: 2 Status: Offline

It was BLK52+ with CFT's and centerline. Total internal fuel 5800 with no imbalance. It was a maximum command roll for 450 degrees. The jet departed and the AOA was low (less than 5 degrees).

Newbie Joined: Jun 10, 2004 Posts: 14 Status: Offline

... referenced a couple old books ... don't know about Block 52's ... do know that the Dash One Chapter 5 for the Block 30 under "Prohibited Maneuvers" includes "consecutive 360-degree maximum command rolls" as a prohited maneuver.

I always assumed this was due to possible aerodynamic coupling problems ... problems with roll coupling or inertia coupling ... I remember some eye opening films of F-8's & F-4's doing some continuous max command rolls & then departing controlled flight ... never thought it was any big deal as there aren't any tactical manuevers I can think of which require consecutive rolls.

call the ball

Geo wrote:

It was BLK52+ with CFT's and centerline. Total internal fuel 5800 with no imbalance. It was a maximum command roll for 450 degrees. The jet departed and the AOA was low (less than 5 degrees).

OK Block 52+ means NSI so my comments about the MCID tests don't apply. CFTs could be a factor, especially in rapid roll rates.

So where did this happen? Edwards? Greece? Israel?

Gums wrote:

This was a serious problem with the older jets, BTW. I speak from experience. A-7D was notorious for 'departures', and I tink the Double Ugly had some bad characteristics unless pilot locked stick between legs and used only rudder to roll.

Dont forget the Navys most Troublesome departure prone aircraft, the F-14. In testing it was proven to be departure and spin prone. Add to this that the original Pratt and Whitneys had a high flame out rate at high AOA. So now we've taken a departure prone aircraft, put it in a low control enviroment, and cut one of its engines creating asymetric yaw forces..... yeah no problems here.

Deffinately some of the magic of digital flight control systems and avionics is spin and departure control. Without it planes like the B-2 would be near impossible to fly, the X-29 would have been a fantasy, and we'd loose a hell of alot of pilots because they did the wrong thing and the plane couldnt bring them out of it.

The F-16 CTF has a deep stall program that all USAF Test Pilot School types get to go through, and used to provide that to the ANG viper drivers (upon payment by the ANG of course). ANG decided they had better uses for the money, and the Active duty never did it AFAIK.

As a TPS FTE, I got to do 3/4 of the departure series. Starts with a glider, moves on to the A-37 (That was quite frankly crazier than the Viper Deep stall ride), followed by the Viper ride. The pilots moved on to the A-7, but because it was single seat, alas us engineers did not get to play.

In the deep stall ride, it proved to be quite easy to depart the Viper, provided you knew the steps. As was pointed out above, you have to assault 2 limiters at once. Example, slow max g turn (I say max G but at these speeds it is stall limited) and then full aileron out of the turn. Little adverse yaw kicks in, the limiters go nuts and the plane goes stupid. Next thing you know your falling straight down, pointed at the horizon. Turns out to be pretty easy to recover (Students, and particularly us ham-fisted engineers, are never put in a config that can't be recovered). Hit the MPO switch and rock it out of that snow bank with alternating push-pulls.

Only trick is to stop pushing when the stall breaks or it can (and often does) flip on over into an inverted deep stall. Easy easy recovery but boy it gets your attention!

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Yaw Departure