a varsity move

[C420sailor]

So random question from a help bubba regarding OCF in a hornet. I have heard that in certain conditions, all displays will show an arrow saying push the stick in what ever direction. Why? Doesn't the AFCS/autopilot/whatever you call it have full authority to move the controls regardless of stick position? Am I missing something?

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The jet immediately drives the leading edge and trailing edge flaps to 34* and 4* down, respectively. This is done regardless of lateral stick position.

Applying full lateral stick with the command arrow engages the ASRM (automatic spin recovery mode), which disables CAS (basically the flight computer 'magic'), allowing full aileron, rudder, and stabilator authority without control surface interconnect.

In other words: PFM.

 

[MIDNJAC]

So random question from a help bubba regarding OCF in a hornet. I have heard that in certain conditions, all displays will show an arrow saying push the stick in what ever direction. Why? Doesn't the AFCS/autopilot/whatever you call it have full authority to move the controls regardless of stick position? Am I missing something?

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Yes, the displays will give you the arrow if the aircraft senses the need to enter spin recovery mode. All that means is that the FCS has sensed a departure (certain airspeed, yaw rate parameters), and by putting the stick in the direction of the arrow, you are giving it consent to 1) revert into DEL (a backup mode of the FCS), and 2) apply flight control surface inputs on your behalf to effect recovery. So in layman's terms, you aren't really doing anything other than telling it to do it's thing. Like I eluded to earlier though, it is challenging to say the least, to find yourself in that situation in the first place.....especially with the most recent FCS software.

 

[C420sailor]

Is DEL a Hornet only thing, or is my NATOPS knowledge just that shitty?

 

[flaps]

have there been many f-18's lost to spins/ ofc ?
my guess is nowhere near as many as tomcats.

also, i suspect mugs probably would not be able to do a similar move in a hornet.

any inputs on how the hornet would behave with similar control inputs?

hard left turn. 350-400 kias
then
hard foward stick
hard bottom rudder.
then
hard aft stick
hard top rudder.

 

[HokiePilot]

So I guess my question stems from : will the aircraft do what ever it thinks is appropriate regardless of stick position? Will the aircraft ever display the command arrow when it is not appropriate?

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[RadicalDude]

Not a stick monkey, but from what I understand, command arrow only displays if the aircraft senses a spin condition, and I don't believe it will recover itself without putting full lateral stick with command arrow.

 

[MIDNJAC]

have there been many f-18's lost to spins/ ofc ?
my guess is nowhere near as many as tomcats.

also, i suspect mugs probably would not be able to do a similar move in a hornet.

any inputs on how the hornet would behave with similar control inputs?

hard left turn. 350-400 kias
then
hard foward stick
hard bottom rudder.
then
hard aft stick
hard top rudder.

I think the Hornet would probably just wallow in confusion......unless you were real fast, like transonic/supersonic, it shouldn't depart from that treatment.....just probably make you very uncomfortable with the unloading and yawing. As for losses, yeah we lost a number of aircraft to falling leaf type departures until a handful of years ago when we got the new software. I don't know statistics, but I generally understood it to be around 1 every year or two. Not as bad as Tomcats I wouldn't think, but it did happen.

 

[scoolbubba]

I know when my aircraft senses a spin condition, mostly because I will fall out of the rack or lose my grip on the red bull / hot pocket. Luckily, the handy dandy spin alarm, known as the NFOs, will be screaming at me, and this will cue me in to the OCF condition. Immediately panic, play possum, and executing procedures will (maybe) save the day.

 

[MIDNJAC]

So I guess my question stems from : will the aircraft do what ever it thinks is appropriate regardless of stick position? Will the aircraft ever display the command arrow when it is not appropriate?

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You shouldn't get the spin arrow unless 1) you manually select SRM which is a NATOPS no-no and also a yellow/black guarded switch, or 2) the aircraft is actually departing. Like I said, I spent a good amount of time doing everything I could to get it to happen, to no avail. Probably somewhat the particular jet I was flying, but it is challenging to do. As for it recovering, the jet will input the controls it needs to in SRM, ie it is doing more than just adding aileron in the direction of the arrow. It ratchets a bit on recovery using the stabs and whatnot, and this is not pilot commanded. The big deal about SRM is that it engages DEL which allows full throws of the flight control surfaces, unimpeded by dampening or other FCC stuff. This is also why the OCF recovery precludes you from doing anything weird with the controls until you are out of the SRM threshold, where the normal CAS FCS logic will resume, and prevent a pilot from getting full throws of the controls in post departure gyrations.

 

[MIDNJAC]

Is DEL a Hornet only thing, or is my NATOPS knowledge just that shitty?

Yeah IIRC it is. We have CAS (normal), DEL (digital and analog) as well as Mech. DEL is basically just a direct link between the stick and the control surfaces, ie you command full left stick and you get the appropriate full throws of the surfaces accordingly. It isn't dampened, or put through the logic of the normal CAS control by wire mode. Analog DEL is just a backup to digital DEL, and does the same thing, though I suppose through backup 60's era analog ferrite core computer assistance. Mech is a pure mechanical link, in which you have limited control of the hyd servos going to the stabs. It really amounts to a combat survival contingency mode, though it can be tripped while single engine if you overload the remaining hyd pump. So basically nothing that you Rhino guys ever have to worry about.

 

[C420sailor]

Bad shit will happen if you attempt to do a negative G roll (forward corner) in excess of 180*. There's a video out there somewhere. The guy finally gets a positive rate of climb well below 1000' AGL.

 

[MPH]

Bad shit will happen if you attempt to do a negative G roll (forward corner) in excess of 180*. There's a video out there somewhere. The guy finally gets a positive rate of climb well below 1000' AGL.

http://youtu.be/wZNaQuUGluk

This?

 

[Catmando]

Interesting discussion. I have spun a number of Navy aircraft intentionally, but I have never spun any naval aircraft unintentially, even though I did a lot of bizarre over the top stuff that would normally induce a spin.

Mugs –who was my hated nemesis back in the day – did teach me the quickest way to roll right was to put the stick to the left... under certain conditions.

Grumman initially said the F-14 would never spin. It didn't for a long time, until a rash of flat spins killed some of my friends. We learned why later. Nevertheless I still flew that thing to incredible limits.

With the airlines I flew both Boeing with standard controls, and Airbus with totally computerized controls. It was a trade-off. Sometimes Boeing would save you by being honest control wise, sometimes computerized Airbus would save your bacon because you may have dicked up. Of course the converse was also true. Pick your poison.

For me, give me a non-computerized flight control, and let me fly!

 

[flaps]

maybe somebody could try this in a hornet sim and report results

hard left turn. 350-400 kias
then
hard foward stick
hard bottom rudder.
then
hard aft stick
hard top rudder.

it might be good not to do it at 1500' the first time.

 

[MasterBates]

I'll go try that in the E-2 sim later. Probably have to turn the engine limiters off to get above 325 thought.

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