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Time and distance to the point of no return (PNR)

(a) time and distance to the point of no return (PNR)

The Point of No Return (PNR) is the greatest distance that an aircraft can proceed and return to ADEP with the required reserve fuel.
After passing the Point of No Return the remaining fuel will not be sufficient for a return to the point of departure.
The flight can only be continued to ADES or to an alternate airfield.

To have a quick look at how to calculate your Point of No (safe) Return,
lets consider a flight from Auckland to Norfolk Island a Distance of around 580nm.
And the aircraft TAS is 200 kts and 4 Hours safe endurance.

No wind

In a no-wind situation it is easy it is the PNR point is just half of your endueance which is 2hours.  2hours at 200kts = 400nm.

A B No Wind TAS 200kts Distance 580nm <- 400 PNR

Auckland to Norfolk Island  (Nil Wind)
Leg Distance  @ Ground Speed = Time
Auckland – PNR   400 nm 200 kts 2 hrs
PNR – Auckland 400 nm 200 kts 2 hrs
Total Time  4 hrs

We loose out when we have wind in to the situation which we always seem to have.

Head wind

A B TAS 200kts Distance 580nm 40kts Head Wind <-<- <- 384 PNR

Auckland to Norfolk Island with a  40kt Headwind
Leg Distance  @ Ground Speed   = Time
Auckland – PNR   384 nm 160 kts 2.4 hrs
PNR – Auckland 348 nm 240 kts 1.6 hrs
Total Time  4.0 hrs

Tail Wind 

A B 40kts Tail Wind ->-> TAS 200kts Distance 580nm <- 384 PNR

Auckland to Norfolk Island With a 40kts Tailwind
Leg Distance  @ Ground Speed   = Time
Auckland – PNR   384 nm 240 kts 1.6 hrs
PNR – Auckland 348 nm 160 kts 2.4 hrs
Total Time     4.0 hrs

Time Required

To work out the time required you need ….

1. Speed, is in Knots which nautical miles per hour.

2. Distance to intend to travel.

In this example we have calculated a Speed of 120 Knots and a Distance of 60 nautical miles to fly.

On the Wizz wheel, Distance is on the out side and time is on the inside.

1. Speed of 120kts on the outside (which is Distance travelled in an hour)

2. so, Time on the inside finds the Hour [60 MIns].

101011111212131314141515161617171818191920202121222223232424252530303535404045455050555560607070808090901. Outer Find Speed of '120'2. Inner lineup '1 hour'

Now we have a Distance and Time Ratio set up you can easily work out the time required as follows

3. Find the Distance on the outside.

4. Read off the Time on the in side.

Notes: easy to work out any Distance and Time relationship

101011111212131314141515161617171818191920202121222223232424252530303535404045455050555560607070808090901. Outer Find Speed of '120'2. Inner lineup '1 hour'3. Outer find '60'4. Inner read off '30mins'

(f) transition altitude

a

18.10.8 Locate a position on a chart.

18.10.8 Locate a position on a chart.
(a) from an NDB given magnetic direction to and distance from;
(b) from a VOR given radial and DME distance.

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18.8.4 Explain how TAS is affected by changes in pressure al

18.8.4 Explain how TAS is affected by changes in pressure altitude, air temperature and air
density.

ETP Quiz

Quizz One

Example of ETP.
You planned a flight with distance of 135 nm
with a 'Ground Speed Out' of 150 and 'Ground Speed Home'100

What is your ETP (Equi-Time Point)?

The Answer is .. ...

Distane to to ETP is : 54
A B Tail-Wind of 25kts -> -> TAS of 125kts, Distance 135nm 54nm <- ETP -> 81nm

Calulate with Nav Computer ... ...

Nav Computer setup
10101111121213131414151516161717181819192020212122222323242425253030353540404545505055556060707080809090GS Home 100GS Out 150+Home 100=250read off ETP = 54 nm locate Distane of 135Note the % of DistaneCheck out [10]
By checking the 1 and read off a percentage distane a long your track where the ETP is.
This a handy check, to double check the ETP has moved toward the wind .
As Double Check, just confirm that the times for each legs are the same.
10101111121213131414151516161717181819192020212122222323242425253030353540404545505055556060707080809090GS Out 150 1 Hour locate Distane of 81read off Time = 32 Minutes
10101111121213131414151516161717181819192020212122222323242425253030353540404545505055556060707080809090GS Home 1001 Hourlocate Distane of 54read off Time = 32 Minutes


18.46.12 Calculate the latest time of departure for a given

18.46.12 Calculate the latest time of departure for a given VFR cross-country flight or a given
leg.
Sub Topic Syllabus Item
Navigation Procedures  VFR

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(b) a Lambert’s conformal projection

a

(a) a Mercator projection

a

18.28.6 Calculate time, speed, or distance, given two factor

18.28.6 Calculate time, speed, or distance, given two factors.

These 3 items are interchangeable eg. If Speed and Time is known, the Distance can be calculated. 

With Distance travelled in a nominated Time, a Speed can be worked out

Distance travelled divided by the Speed gives us a Time