Prop Bending Forward on Take Off (digital camera artifact)
Diversions and lost procedures often cause students grief on the private check ride because they are high work load items. High work load items are not an uncommon occurrence for the pilot. For example, the instrument approach is a high work load item. There is a lot of preparation and situational awareness activity on the pilot's part to make sure that the approach is successful.
Executing a lost procedure for real is also a high workload activity with added element of fear that comes from not knowing where you are located (how much fuel do I have? Do I fess up? Help!).
Once you are beyond an initial difference, lost procedures and diversions are one in the same activities. The initial difference is that with the diversion you know where you are located on your flight plan (we hope) and for the lost procedure you do not know your location. Once your location is known, processes for a successful outcome are identical: turn the airplane towards a desired position, estimate time and fuel required to get there. The lost procedure is covered in all basic aviation texts. You start by circling, climbing and determining your position. Circling keeps you over the same place. Find a ground reference and keep it in sight. A barn, a pond, etc. work fine. In short, if you don't know where you are at, don't go somewhere else - keep your present position. A circling strategy for most small GA aircraft is to reduce power (around 2200 RPM in most 160-180 horsepower engines)and attain an airspeed of around 90 KIAS. Add necesary power to keep 90 KIAS, but don't get carried away because you are trying to conserve fuel and you aren't going anywhere because you are lost. Bank about 15-20 degrees which tends to form a rather stable bank and do a gentle slow climb. You can do a faster climb with more power if you know that mountains will block VOR reception. You climb to see more things and get better radio reception. If you see something you know is on the chart, point the aircraft at that object until the magnetic compass is stationary and note the heading on the compass, then resume your position hold by restarting the bank you had a moment ago. If you use the reciprocal of the direction to the object you aimed at, you can draw a line of position (LOP) on your chart from that object. You are on this line. A VOR radial will do the same. Crossing two LOPs or using a radial and a range (DME value) will allow you create a position on your chart.
Ok, now we are past the initial difference. From this point on the diversion and the lost procedure are the same.
1. Determine where you wish to go from here - the desired position
2. On your chart, position a straight edge between current position and desired position
3. Obtain the magnetic direction to the desired position (see below)
4. Turn the aircraft towards the desired position and maintain the determined magnetic direction using your heading indicator (make sure your HI is correct!)
5. As soon as you turn from your known position, start a timer
6. While enroute to your desired position, determine the amount of time and fuel it will take to get there. Can you make it? No, then start circling and come up with a better plan
7. If an airport is your desired position, then start preparing - see below
Obtaining magnetic direction:
The best device I have seen for this purpose is a multifunction tool one my students devised to simplify the determination of direction, time and fuel. It is a transparent straight edge. Note that distance, time and fuel are linearly related to each other for a given airspeed (at a given power setting). My student used indelible ink to tick off 5 NM increments on the rule (sectional scale in her case). On a row immediately below each 5 mile tick, put amount of fuel consumed and on another row below that put time in minutes.
Ok, I realize that "speed" really means ground speed. If you use the ruler in a no-wind situation, it will tell you how far, how much fuel and how long with no math - one value below the other. If you know that you will encounter head winds (or tail winds) estimate the percentage difference. For example, I expect to fly over the ground about 10% slower than my true airspeed. This means you add about 10% to time and fuel. Of course, if you have an air data computer on board, use the wind/ground speed data to estimate the effects of wind. If you only have a GPS, start heading to the desired airport and once you have cruise airspeed look at the estimated time enroute value (ETE) and reassess remaining fuel - will you make it?
Borrowing from marine charts, magnetic direction is obtained by lining up your straight edge on your current position and your desired position (creating a desired track). Taking great care, move the straight edge towards a VOR magnetic rose keeping the edge parallel to the desired track (mariners use parallel bars). Obtain your magnetic heading off the VOR rose. With some practice it is amazing how accurate this can be as long as your ground track is reasonably short (perhaps less than 25-30 NM).
Preparing for an unplanned airport after departing from a known position
So far, so good. Now the workload really starts. Here are the essentials perhaps in the correct order:
1. Obtain the CTAF and automated weather frequency if available
2. Obtain the automated weather or contact the UNICOM or traffic at the airport to get traffic/pattern advisories.
3. Determine pattern altitude at the airport
4. Determine other pattern characteristics (left, right, obstructions, etc.)
5. When do I start my descent? Do I intend to overfly the airport at TPA+1000' to inspect windsocks and runway conditions or will I want to be at TPA 2-3 miles from the airport? Use the 4 NM/1000' rule of thumb for descent planning purposes. If you are at 5000' MSL and you need to descent to 1500' MSL subtract: 5000-1500 = 3.5 thousand feet. Multiply: 3.5 * 4 = 14 NM. This rule of thumb is based on a 120 kt ground speed and a descent of 500'/minute. If you plan to be at 1500' at the airport, then start the descent 14 NM from the airport. If you plan to be at 1500' 3 NM miles from the airport, then offset the descent slope by 3 miles and start at 17 : 14+3 = 17 NM.
6. After how many minutes from my departure point will I cross 10 NM from the airport? Announce my intentions on the CTAF to airport traffic at 10 NM, or have a handy 10 NM easy to identify ground feature in mind to clue you when to report. This can also be a VOR cross radial. If you are using GPS then look at the distance to destination value
7. Estimate how and where you will enter pattern before you arrive
8. Estimate a drop dead time - I missed the airport and it is behind me. Start another lost procedure process and find the airport from this new position. Another procedure is to use a "sentinel" which can be anything that "guards" the backside of your route. A VOR radial, a highway, a railroad, etc. Once you have crossed your sentinel, you know you missed the airport - stop, do not keep going.
The Main Message
The lost procedure and diversion are both high workload activities and can lead to significant stress, especially if you are lost because of the fear factor, and in both cases you have likely opened yourself to unknowns such as new airports, new terrain, will I have enough fuel, etc. Success depends on your ability as a pilot to keep a cool head and carefully follow the recipe (a procedure) for success. Using a diversion or lost procedure check list is a good idea. Success in all aviation high work load situations have the same demand: a cool, analytical head and clean execution of the proper procedure, one step at a time.
