Diversions - "Variation or departure from the natural condition"

As I'm getting ready for my first cross country, there are a few things that have to be covered including diversions. So what are they? There could be many reasons for the need to 'divert ' from your intended path, including deteriorating weather conditions, aircraft problems, sick passenger or hysterical wife...;) The bottom line, we need to learn how to change course. For more details visit your Flight Training Manual, exercise 23 on p 144.


Procedure

1. Setup
   
• Locate your departure position
• Get into Orbiting/Patters - either square or long rectangular. The benefit of the rectangular is you have to do only two 180 degree turns - hence more time to plan
  
• Get to a clean configuration speed of 80KIAS (or 10 degree flaps, you don't want to be too slow as stall risks increase
• Brief the Passengers
2. Plan a Leg - using a VNC map (1:500,000)
• Draw a track line (True track)
  
• Obtain a Magnetic Track
  
• Use VOR compass rose or
• Lines of longitude
• Direction is obtained be estimating the angle of the track line intersects the line of latitude and longitude
  
• Apply the magnetic variation to obtain magnetic track - TIP--> WEST is BEST, therefore add the variation to your true track e.g. 11W variation and your true track of 200 degrees, therefore the magnetic track is 211 degrees
  
• Estimate Distance
  
• Tip - measure distance between your pinkie and thumb with the two fingers extended outward. Then measure the distance on a ruler with the correct scale. My distance is 50 nm. Then do the same with your four knuckles (20nm) and finally your thumb ( in my case 5 nautical miles) - this will help you estimate the distance very quickly!
  
  
• Another method is using the lines of latitude - remember that each minute of latitude marked on the map happens to also be one mile.
  
• Set Speed
• Tip - set your indicated airspeed to 90 KIAS
• Reason - when the time comes to estimate time (next point), it will be easy to estimate the time on-route using the 2/3 rule. For instance 2/3= 60min/90KIAS therefore if you know you have traveled 12 nautical miles at 90KIAS, this means it will take you 12/3 * 2= 8 minutes to get there
  
• According to the Flight Training Manual they want you to estimate your ground speed first
  
• With no wind conditions your true airspeed (TAS) airspeed will equal ground speed
• With head wind: e.g. 20KT head wind and your TAS is 100KT then your ground speed becomes 80KT or 100KT-20KT=80KT
  
• With a tail wind: 20KT tail wind and your TAS is 100KT then your ground speed becomes 120KT or 100KT+20KT=120KT
• If the wind is at approx 45 degrees to your direction - assume head or tail component of about 2/3
• The challenge with the above is that you need to calculate your TAS using your computer (E6B) plus you need to assume the winds have not changed since your departure which may be presumptuous.
  
• The method I describe above is more practical in my mind as it relies on simple time measurement and distance estimate based on your current position. It is definitely more convenient considering the time restrictions...
  
• Time en-route
  
• look above to help you estimate the time using the 'indicated airspeed' method.
  
• The simplest is to divide up the leg into equal parts so you can have simple checks when you fly the leg. So if in 5 minutes you flew 10 nm, then if this is the half point, you have another 5 minutes to go...
• Fuel Burn (Fuel required) - for Cessna 172 you may use 10 gallons per hour as a rule of thumb, or 5 gallons per 30 minutes or 2.5 gallons per 15 minutes. This will help you estimate if you have enough fuel for the diversion. Check your POH for details regarding fuel burn. Always round up to be sure...So if the recommended fuel burn at a given situation is 8 gallons, round it up to 10 gallons etc.
  
• MEF (Maximum Elevation Figure) Ensure your altitude is set at well above the max elevation figure to clear any obstacles by at least 1000 feet. For more info on MEF go here .
  
  
  
• Mark a Half Way Point at which you will:
• Do a location check
• Fuel check
  
• Time check
3. Departure
• Set the Airspeed and proper power setting i.e. 90 KIAS when at set altitude
• Set HI (Heading Indicator) to Compass
• Lean Mixture
• Make a radio call (126.7 - London Radio) - make others aware of your intentions plus also ensure if you were on a flight plan to notify appropriate ATF
  
• Note your time!
  
• Departure Angle Check (DAC) - are track and visible landmarks correct based on the initial setup? Ensure you are where you think you are.
4. En-Route
• Navigate
• Half Way Point - are you where you thought you ought to be? Drifting?
  
• Look for at least 3 things on the map to help you identify the location - e.g. island just a few miles of port side on the lake, town to the right and two towers just ahead
• Plan for your arrival - check airport ATIS if available, call traffic, review the CFS to review the runway details, obstacles etc.
• Follow low level navigation - as the weather may deteriorate, you may need to fly at lower altitudes making the navigation a bit more challenging due to restricted view angle, faster approaching landmarks etc. Therefore choose very distinct landmarks such as railway lines, roads that cross the railway lines...Keep an eye out for terrain changes especially elevations unaccounted for!
• If you get lost switch from "watch map to ground" to "watch ground to map", meaning you need to find something distinguishable on the ground and then finding it on the map. You may also help yourself with a "circle of uncertainty" which is basically a circle (radius of a 10% of estimated traveled distance since last known point) .
  
• E.g. If you have flown 10 minutes at 120KT since your last known position, you will have covered 20 nm (2 miles a minute or 120/60 X 10min), draw a circle 20 miles from the last known point along the intended path with a radius of 2 miles...That 2 mile area around your current position is where you have to find the next distinct landmark...

Some other tips include

• Use a checklist - during the flight exam, you may now want to whip it up at the beginning as you want to show you 'know' the procedure, but after you complete the first step it may be seen positively by the examiner that you are also prepared.
• If lost, don't be afraid to admit you are lost. Don't let your ego lead you. Fly for something obviously distinct to find your location. Climb if possible as it will give you greater visibility and radio range.
  
• Radio it in with location, fuel qty, request radar assistance etc
• In case of extreme emergency radio in MAYDAY at 121.5 MHz and in case of seriously deteriorating conditions consider a precautionary landing
  

The above seems like an awfully long procedure, that is why I will have to revisit and practice a few times. I will probably also create a checklist just to have the main points down.

Next on the menu will pilot navigation. Stay tuned.