Wednesday, October 21, 2015

AoA, EM, and Staying Ahead

We were going fast as we descended into right downwind. For spacing, the tower controller instructed the pilot to extend downwind, adding that he would tell the pilot when to turn base. Realizing this was not a standard traffic pattern by any means, the pilot began to catch on. He reduced power "to slow things down" and then added flaps. The pilot's chosen downwind heading had us drifting inward and the turn to final was going to be tight. The addition of flaps combined with the reduction in throttle while maintaining altitude caused the airspeed to gradually decay. After the "base turn approved" call came, the pilot realized he was overshooting final. He entered a steep, coordinated turn and the LEDs on his angle of attack (AoA) indicator, which had started to illuminate earlier, suddenly lit up in holiday fashion. Startled by the little string of red lights, the pilot promptly reduced the aircraft's pitch - an excellent choice. After an uneventful landing, I asked him to debrief what happened. The pilot explained the AoA indicator had warned him the wing was close to stall, so he reduced the aircraft's pitch as he continued the turn. He added that he was glad he had installed the AoA indicator since it had just helped him avoid a potentially deadly base-to-final turning stall close to the ground. I couldn't argue with the end results, but wasn't sure he understood how his energy management choices led to him approaching the critical AoA in the first place.

Having flown with a half dozen or so pilots who have installed AoA indicators, it's clear that they can be useful devices. There are annoyances, of course. Listening to them drone on "Too slow, Too slow" while in the landing flare is tiresome and distracting. And some pilots can become fixated on the AoA indicator during approach to landing, trying to get just the right number of LEDs illuminated in hopes of nailing the perfect landing. Yet in spite of their limitations, if AoA indicators help prevent stall/spin accidents then one could argue that they are valuable.

You don't need an AoA indicator installed in the aircraft you fly to cultivate a conceptual understanding of energy management (EM). Energy is what allows an aircraft to fly and keeps it flying. Understanding EM begins with recognizing the total energy currently available, the energy required for the current phase of flight, and (perhaps even more important) the energy that will be required for the upcoming phase of flight.

Energy for flight comes in several flavors: Airspeed (kinetic), Altitude (potential), and Engine power/thrust (chemical). Sometimes we get a boost from nature in the form of updrafts and sometimes nature increases our energy requirements in the form of downdrafts or heavy precipitation. The phase of flight (straight and level, climb, decent, turning, fast cruise, or slow flight) and aircraft configuration (gear, flaps, speed brakes) determines how much energy we need too keep flying. Before a pilot makes any adjustment to their aircraft's energy state, they need to account for the energy available and the energy required to determine if they have a surplus, a deficit, or if things are just about right. Once a pilot grasps their aircraft's current energy state, they are equipped to think ahead: What do you want the aircraft to do next and how much energy will be required to meet that goal?

You don't have to look very far to see that human beings tend to prefer simple answers to complex questions, but you can't reduce EM to a simple maxim or two.  To appreciate EM you have to embrace the dynamic interaction between the various forms of energy available for flight, the aircraft's configuration, the load on the aircraft created by turning flight, the angle of attack required for the desired airspeed, and then synthesize a plan for managing the energy so it's just right. It's so much easier to just fly a profile of canned settings or make things up as you go along. Perhaps this explains the distracting pitch versus power debate than so many pilots and instructors seem to be mired in. It's pitch plus power, plus drag, plus configuration, plus load factor = desired outcome.

Back to the starting example. My response to the pilot's self-critique was that the crux of his excess energy problem started several miles and minutes earlier when commenced his descent. Without a reduction in engine power, the act of descending produced a significant energy surplus. That lead him to descend into the pattern with excess kinetic energy (airspeed) and in a clean configuration no less! The controller gave the pilot an extended downwind, perhaps in part to account for the aircraft's excess airspeed. When the pilot caught on and recognized he had an energy surplus, he chose to do two things at once: He reduced engine power and added flaps. The cumulative effect of these two changes was a gradual decrease in kinetic energy. The slower airspeed required a increase in angle of attack, which in turn increased induced drag. That drag, combined with the drag created by the flaps, gradually increased the energy required. He went from having too much energy to not having enough energy.

When a steep bank was required to turn onto final, the energy required increased further and only then did his AoA indicator start barking at him in earnest. The pilot's response to the AoA indicators warning was to reduce the aircraft's pitch, which reduced the load factor, reduced induced drag, and traded altitude (potential energy) for increased airspeed (kinetic energy). The takeaway here is that the AoA indicator couldn't warn the pilot about his earlier, dubious EM choices.

What the pilot could have done differently was, before descending, to take some time to evaluate how much altitude was going to need to be lost to get to pattern altitude, what the airspeed was before entering the descent, and how much time (distance) was available to consume the potential energy. This sort of strategic "thinking ahead" is more complex than deciding it's time to descend, then just pushing the stick or yoke forward and accepting (or ignoring) the consequences.

There's no doubt that AoA indicators have saved lives and will continue to do so. It's pretty clear that they can warn pilots that they are close to running out of energy. These devices also raise important questions for flight instructors. Just how good a job are we doing teaching pilots to conceptualize energy available, energy required, and to plan ahead for what's going to happen next? This is a perfect example of correlative knowledge - taking several variables into account and coming to an understanding of how to manage all those variables.  Give a pilot an AoA indicator and they can avoid getting into an inadvertent stall. Give a pilot a conceptual understanding of EM and they'll do more than just stay out of trouble, they'll become a more skilled and safer pilot.

Sunday, October 11, 2015

Assembling a Redbird Simulator

Have you ever wondered what it would be like to assemble a Redbird simulator? It is a fascinating process and here are some photos that show the assembly of a CE510 Mustang simulator at the Bay City Flyers site in Hayward.

Delivery truck, in position

Our simulator room, carefully measured many months ago ...

Yokes come off so the console will fit through a narrow doorway

Lot's o' Boxes

Beginnings of the motion platform
Motion platform coming together

The cradle will rock!

Flooring secured

Adding motor, attaching drive belts

Not quite done with the heavy lifting

Bolting console in place

After measuring, adjusting, and tweaking, the motion platform is functioning

Rudder pedals added

Left side panel, O2 mask, and circuit breakers

Right side panel, circuit breakers, seat rails ...

Visual system monitor racks in place

Needs some walls

Fits like a glove

Coming together

Need a roof ...

And a rear wall ...

Looking like a sim

Calibrating and testing

Finished product. Fits perfectly!
Many thanks to Nathan, the hardworking and talented Redbird technician who directed two neophytes in helping to assemble this simulator. Now it's time for Mustang pilots to put it to use for their 61.58 recurrent training.

Wednesday, September 02, 2015

September 2015 Photos

I know it's been a while since my last post. Very busy, but here are a few photos until I can get around to a couple of posts I've been meaning to make.

Hold short of taxiway charlie

Well, maybe not that short ...

Playing with EVS

Pinnacles National Park at sunset

Walk into town means crossing the runway. Really?

En route Bellingham

Boiling atmosphere

Over Puget Sound

Interesting weather for CA summer

DA42 Dash 6 near SF Bay

Early morning IFR departure

Stratus and forest fire smoke

Chock it up to experience?

En route KSNA

Dodging TSRA

Passing jet traffic on left, really small

Waiting at St. Louis-Lambert ...

Embedded TSRA

More instability

When FL400 doesn't get you on top ...

Westbound in the flight levels: Headwinds and sunburn

More TSRA ...

More boiling ...

There's a way through or around

Night flight home