
True Air Speed (TAS) = 90kts.



Note: If the temperature is not standard for the altitude then use the AIR SPEED window to align the C.O.A.T. against the PRESSURE ALTITUDE. E.g. if the temperature at 5000ft is not the standard +5˚C but (say) +20˚C (ISA+15 see iv. above - Standard Atmosphere) the T.A.S. will be 99.5kts. The higher the temperature the higher will be the T.A.S because the Density is lower at that altitude. +20˚C at 5000ft altitude equates to a ‘Density Altitude’ of 6800ft. Conversely -20˚C at 5000ft altitude equates to a ‘Density Altitude’ of 1950ft.
Here is a definition of DENSITY ALTITUDE: The altitude in the Standard Atmosphere corresponding to the flight level density. Basically it is the measure of the number of molecules of air per cubic metre which can act upon the aircraft surfaces with the resulting forces of lift, drag etc. Density of a gas is determined by pressure and temperature. Density Altitude is the theoretical density of a standard atmosphere at that altitude. Aircraft performance is directly related to air density; therefore, performance is determined by DENSITY ALTITUDE regardless of the actual altitude.OK – that is TAS out of the way!

TAS:

(Click on the image to ENLARGE.)
When the aircraft is above 300ft AAL lower the nose by a small amount to allow the aircraft to accelerate slowly. When the ASI reads 60KIAS minimum raise the flap to zero-degrees, i.e FLAPS UP and re-adjust the attitude for a 65KIAS climb (CLB). Again, Power - Attitude - Trim. The power has not changed, but the attitude has and so has the configuration (Flaps 10 to Flaps ZERO). Attitude flying and correct trimming are the answer to accurate and efficient flight. Do not chase the instruments, but LOOKOUT and use the visual horizon to adopt the correct ATTITUDE. Only when the attitude, speed and the power are stabilised do you TRIM. Do not 'trim' the aircraft into the attitude - this is a COMMON ERROR and useless! Roll the aircraft into a 15-degree angle of bank climbing turn. Keep the aircraft balanced by maintaing the BALL in the middle and adopt a slightly lower pitch attitude in order to maintain the correct cimbing speed of 65KIAS (67KIAS @ S.L. reducing to 61KIAS @ 10,000ft AMSL). Do not trim for the turn, but anticipate the rollout by approx 1/2 of the angle of bank (AoB). You know what the wind direction and strength is (approximately), so apply the drift angle using the max drift method to fly a correct crosswind HDG. Continue the CLB to circuit height (typically 1000ft AAL). Anticipate levelling off by 10% of the rate of climb (RoC) or vertical speed (VS). VS = 500FPM = 50ft anticipation. Make a level 30-deg angle of bank turn onto the downwind track. Leave the power at full power until the aircraft reaches cruise speed (CRZ SPD) of 90KIAS. As the aircraft accelerates towards CRZ SPD progressively and gently pitch down - Progressively Adjust Attitude - until the IAS and the altitude (ALT) have stabilised. Now reduce the power gently to CRZ POWER of 2150RPM. ATTITUDE - POWER - TRIM. (HDG = TRK +/- Drift Angle. Now TAS will stabilise at approximately 90KIAS, so max drift will be 60/90 X WS). Fly Straight & Level downwind.
I am often asked the question, "Should I use the 'wind UP' or the 'wind DOWN' method when solving the problem of finding Heading and Groundspeed on the "Dalton" navigation computer? Personally I use a Jeppesen CR-5 Computer which solves the wind triangle trigonometrically and you can put the CR5 in your shirt pocket. I also have a beautiful AristoAviat 617 which has a rotary indicator for the wind. Both of these instruments are EXCELLENT for accuracy. I am attaching the R.A.F. teaching (at least it was the teaching when I was in the air force a long time ago) which should clarify any queries you may have. Nothing has changed since then, but do also study the USER MANUAL that comes with your flight navigation computer. The important facts to remember are: HEADING (HDG) is on the same vector as TRUE AIRSPEED (TAS) and TRACK (TRK) is on the same vector as GROUNDSPEED (GS). Like oil and water, they do not mix. The conventional PPL navigation problem is to find HEADING and GROUNDSPEED. You have measured the TRACK and you have downloaded the WINDS for your planned flight from the Met Office (Click here for the Met Office weather & winds). So you know the track and you know the wind. We will have to assume that you also know the True Airspeed. TAS will be addressed later (see Ex 18 (v)). Paragraph 12 of the R.A.F. Notes addresses the problem of finding the HEADING and the GROUNDSPEED neatly (although you will note the TAS is 350kts - those were the days!! not a mere 90!
!), but please read everything
up to, and including Paragraph 12. Click on any image to ENLARGE.
