The average wind applicable to a direct flight from Winnipeg (CYWG) to Brandon (CYBR) at 5,500 ft would be (1) 290°M at 30 kt. (2) 290°T at 30 kt. [...]]]> A commenter on a post regarding the PPL tests had trouble with the following question:

The average wind applicable to a direct flight from Winnipeg (CYWG) to Brandon (CYBR) at 5,500 ft would be
(1) 290°M at 30 kt.
(2) 290°T at 30 kt.
(3) 310°M at 31 kt.
(4) 310°T at 31 kt.

FDCN CWAO 061920
ISSUED 1200Z 07 FEB 2007 FOR USE 6-17Z

	3000	6000	9000	12000	18000	24000
YWG	2825	2728-07	2932-10	2935-15	2939-26	2841-38
YBR	3030	3132-06	3133-10	3135-15	3041-28	2948-40
YYQ	3529	3428-13	3229-14	3130-19	3032-32	2733-42
YYL	3327	3435-10	3338-14	3337-19	3136-31	3038-44

He got as far as interpolating the wind speeds and directions at 4,500 feet by averaging the respective values but did not know how to proceed after that. Here is how I solved it:

The pertinent information is as follows:

Between 6,000’ and 3,000’ there is a difference of 3,000’. The altitude required is 5,500’ which is 2,500’ above 3,000’ (or 500’ below 6,000’ depending how you look at it. For the purposes of this example I will be using the 2,500’). There are two steps to this problem:

1. Find wind speed and direction at the required altitude at the respective airports.
2. Average them to find the the average wind.

Step 1: Finding wind speed and direction at the respective airports

I will show you the calculation for YWG. Follow the same steps to find the values at YBR.

Wind Direction Adjustment = (270 – 280) * 2500 / 3000 = – 8.333…
Wind Speed Adjustment = (28 – 25) * 2500 / 3000 = 2.5

Wind Direction = 280 + –8.333… = 271°
Wind Speed = 25 + 2.5 = 27.5 kt

At YBR the wind direction would be 308° and wind speed would be 32 kt.

Explanation: Finding the wind at non-reported levels is simply a matter of properly interpolating the information you are provided. In this case I used a weighted average to give me the values I needed. One thing to keep in mind with this calculation is that order is important. The order I followed was going from 6,000’ (I took the values here) to 3,000’ (subtracted these values) then back up to 5,500’ (multiplied by the weight, 2,500/3,000 and added to the values at 3,000’).

Another way to think about it is you will be going 2,500 / 3,000 = 83% of the way from 3,000’ to 6,000’ so you add 83% of the difference between measurements at the different altitudes to the values at the lower altitude (or you subtract 17% of the difference from the values at the higher altitude).

Step 2: Average wind

Average wind direction = (308 + 271) / 2 = 289.5
Average wind speed = (32 + 27.5) / 2 = 29.75

With rounding, the applicable wind is from 290 at 30 kts. Keeping in mind that the FD reports directions in degrees TRUE leads to the correct answer being (2) 290°T at 30 kt.

Notice that these calculations assume the change from one altitude to another is linear which may not always be the case.

How would you have solved it? Leave your reply in the comments!

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1. The view from the control tower

 Location: Telluride, Colorado Airspeed: 180 kts Altitude: 12,000 ft MSL

Co-pilot: "Center, ABC has airport in sight."

Center: "ABC, [...]]]> I would like to share with you two recent situations I found myself in while flying around to illustrate the fact that, as a pilot, you can’t let your mind wander even for a minute.

 Location: Telluride, Colorado Airspeed: 180 kts Altitude: 12,000 ft MSL

Co-pilot: "Center, ABC has airport in sight."

Center: "ABC, Tower, radar services terminated, suggest you switch to advisory on 123.45."

Co-pilot: "123.45 for ABC." To me: "OK we’re on final, slow down to 140 kts and drop full flap."

I retard the throttle lever and wait for the airspeed to start decreasing. It doesn’t. "Alright," I say to myself, "raise the nose a bit, maybe it’s too low." The airplane begins to climb, airspeed changes slightly. Set throttle to idle. No change, we’re still climbing.

At this point I paused FSX and enter its controls configuration. I test out the control axes, everything is fine. Back in the cockpit I unpaused the simulation and hit the flaps, they deploy courageously against the airflow. I look at the throttle quadrant as I move my throttle lever back and forth, nothing. I then snap the view back to forward and incredulously look at the FD (Flight Director) light as it glows back at me as if to taunt me. I flick the switch off and I am again in control of my airplane. I slow down, land (luckily it was a long final leg) and taxi off to meet the limos waiting for my passengers.

 Location: 2 nm west of Paris, Ontario Altitude: 3,500 ft MSL

The second anecdote I wish to relay happened during a recent flight while doing some upper air work. My instructor asked me to enter into and recover from a power off stall. For those of you not aware with the manoeuvre, I reduce throttle to idle and pull the carburetor heat on then attempt to maintain altitude by raising the nose. As the airspeed decreases I raise the nose until I feel the buffet indicating a stall. The nose then drops and I recover; it’s a manoeuvre I have practiced many times before.

That’s the theory, in practice this time however there was no buffet or nose drop. Here I am with the nose about 25° in the air, the stall horn going off, air speed hovering around 40 kts waiting for the signature buffet and nose drop. My instructor asks me if we’re stalled. I have to think about it: "Are we stalled? This doesn’t fit what I’ve experienced before. Is this a stall?" Finally, I look at the VSI and altimeter and sure enough we’re descending, and fast. Nose forward, full power, carb heat in and recover from the dive. Emergency avoided, lesson learned.

Lessons

Know the airplane you’re flying and its systems

In the first instance I was flying a Learjet on approach to Telluride airport in the FSX Mission “Telluride Landing.” I had turned on the flight director before the autopilot by setting an airspeed to be maintained. When I turned off the autopilot I did not bother to check that all the lights on the panel were off. Also, I am not familiar with the aircraft and its systems. I’m sure a real Learjet pilot/captain would know that the flight director would stay on. I, on the other hand, just picked the mission and started flying it.

Not all the symptoms of an emergency need to be apparent

When I had previously practiced stalls the chain of events went something like: power off, raise the nose, raise the nose, raise the nose, buffet, nose drop, recover. That’s what I was expecting from a stall, but that’s not what happened. There was no nose drop or buffet, the plane just started falling from the sky smoothly. The only indication of a stall I had was the stall horn going off and that should have sufficed. Instead, by waiting for the other symptoms, I wasted about 500’ of altitude and that could have cost me dearly.

Even with an instructor in the right seat, you’re in control (unless told otherwise of course)

Don’t use your instructors as a safety net. They won’t be there after you have your licence and you must make your own decisions (aka pilot decision-making).

Practice, practice, practice

I can’t have a post about lessons learned without this one. You must practice the exercises you go through while training. There’s a reason you have to know it for the test and, unlike some things learned in school, you can’t forget them once you pass. At least once a month if not more often, grab a plane and go through some of the upper air work. It will benefit you.

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