By lex, on December 9th, 2009
I’ve flown in the last few months with a pair of young commercial pilots working on or having recently completed their Certificated Flight Instructor qualifications (Question: What’s the difference between a CFI rating and a pepperoni pizza? Answer: You can feed a family of four on the pizza.) As a part of the dog fight introduction I always introduce steep turns – two g’s, 60 degrees angle of bank.
For most general aviation and even for the commercial pilots, 60 degrees AOB is a lot (most non-flyers don’t know the difference). But each of my recent passengers who were already rated were surprised at how easy it is to maintain level flight at 60° AOB. There’s nothing to it, as I show them: Just keep the horizon – the real one, not the “artificial” horizon on the instrument panel – cutting through the same spot on the engine cowling and she has to stay level. If you start seeing more ocean than air, you’re descending. More air than ocean you’re climbing. A little opposite rudder fixes everything until you can correct your g-loading or angle of bank. In a level turn, the two are inextricably and mathematically intertwined: 60º = 2 g. 90° = ∞ g. When your entire lift vector is orthogonal to the gravity vector, you can rip the wings straight off her and she’ll fall to the earth at 32 feet per second2.
There’s not much reason for a GA pilot going from here to there to pull two or more g’s. Unless he sees something right ahead that he doesn’t want to hit, in which case the more the merrier, up to the airframe limits. In which case it’s good to know that you can put a good turn on, with sufficient airspeed, to get out of the way.
Sufficient airspeed, of course, is key. She stalls at a higher speed under g-loading than she does in the landing pattern. You can’t get out of the way of nearly anything, once you’re stalled.
They introduce us gradually to steep turns in Navy flight training. When I first started out in T-34s, you approached the field by flying up the starboard side of the runway and then making a left to downwind at 30° AOB. By the time we got to formation and acrobatic flight, we were authorized – required even – to use 45° AOB. And there we pretty much stayed until basic jets. When we were taught to “break” to downwind.
At all of 60° AOB and 2g. No more. No less. Points off for gaining or losing altitude. The break turn being level, like.
Definitionally. Whose point it is, at it’s core, to burn off your excess smash and get you down to landing gear extension speed.
It’s easy for the student or novice to focus too much attention on the altimeter or vertical speed indicator, both of which are pressure instruments and therefore lagging performance indicators. It’s easy as well to over-control the bank angle on the attitude reference indicator trying to correct, and far too simple to turn a gradual descent into an egregious climb or vice-versa. At least until the light comes on and you either figure out for yourself – or some generously talented instructor pilot tells you – that the best artificial horizon in the world is the actual one. Right outside the canopy there. Keep that actual horizon marching through the same place on your canopy in a steep turn and you can’t descend (or climb). At least until you run out of g available. Which is generally far short of the infinite number required at 90°.
Required g loads increase rapidly as bank angle increases, being inversely proportionate to the cosine of the bank angle. You’re (most likely) straight and level under 1 g right now (VX possibly excluded). It only requires 1.4 g to remain level at 45° AOB, and as I’ve already mentioned, 2 g’s to remain level at 60º, but it takes nearly 6 g’s to stay level at 80°. Eighty to eighty-five degrees is where it starts to get sporty.
It takes two things to generate g loading, airspeed and back stick. At speeds below “corner” airspeed – Va for those uninitiated into energy/maneuverability diagrams – you’ll stall before you get to maximum g. At speeds above corner airspeed, it’s possible to over-g the aircraft before you reach stall speed. Especially if you’re a plumber.
So the faster you go, the more g available, the steeper your bank angle. Which, by the time you get to advanced jets, is quite a temptation. Because hauling the chilly into the break and making a good turn looks good around the field.
And it’s better to die than look bad.
The real temptation comes in the fleet, once you get out fumunda the eye of the iron guard instructional cadre. Whose purpose it is to find fault.
(I remember coming back to the FA-18 after my adversary tour in Key West as a lieutenant commander. Flying in the trunk with a young lieutenant instructor pilot on a ferry flight. Clearly not knowing who I was, or what I was about. As we came towards the initial, I could sense his indecision.
“I bet you can’t knock me out in the break,” I challenged.
I felt, rather than saw the grin on his face under the O2 mask. Saw, as well as heard, the throttles creep up towards the stops. Felt, in the very bowels of my being, the 7.5 g’s he put on in the break to downwind. Came out of the turn to downwind with fluid filling the pleura in my lungs and laughter in my heart, as I coughted to him, “I win.”)
But years previously, as a student, the iron guard was there to keep me straight. And after one day, when I’d come into the break carrying too much speed and exceeded the prescribed 60° AOB and 2 g, there were the two long-faced instructors asking me what I had been a-thinking of? Coming into the field with all that smack on the jet.
“What’s the point of speeding up only to slow down?” the first asked me. The second nodding sagely.
Your humble scribe kept his own counsel, which was a hard challenge for him in those days. Thinking as he did, what?
Is this a trick question?
Because the answer was, as they very well knew, “It’s fun.”
It’s a serious business. It doesn’t have to be a grim one.