Nav ?
Thread Starter
Joined: Mar 2000
Posts: 14
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Nav ?
Help ........ with a Nav question pse:
If you follow a constant heading from a free gyro ( not corrected for E Rate ) - what path do you follow over the earth´s surface?
ans:. .a. Gt Circle. .b. Spherical Path. .c. St Line on chart etc etc.
Favourite ans wd seem to be Gt Circle. If so, cd someone pse explain why??
Thanks in advance.
If you follow a constant heading from a free gyro ( not corrected for E Rate ) - what path do you follow over the earth´s surface?
ans:. .a. Gt Circle. .b. Spherical Path. .c. St Line on chart etc etc.
Favourite ans wd seem to be Gt Circle. If so, cd someone pse explain why??
Thanks in advance.
Jet Blast Rat
Joined: Jan 2001
Posts: 2,081
Likes: 0
From: Sarfend-on-Sea
If the gyro is not corrected for Earth rate, then the path followed will be irregular. It will depend on latitude, speed and direction travelled. This however is not within the scope of the ATPL nav syllabus, so don't panic! If you had heard this as feedback, then someone has their feedback confused.
If you still want an explanation :
A gyro that is not corrected for Earth rate develops an error at a rate depending on latitude (and therefore the direction and distance you have travelled). Direction actually tracked depends on the error, and that error is changing on a daily cycle (actually a 23-hour-56-minute cycle!). Therefore the error at a given point on a track depends on how long you took to get there, and so on your speed. This is of course all compounded by transport drift, and is beyond any but a fairly competent mathematician (rather beyond me!) and certainly beyond the retired RAF navigators who write the learning objectives and most of the questions
!
If you have any further questions feel free to email me - I was nav instructor at SFT until their fall.
If you still want an explanation :
A gyro that is not corrected for Earth rate develops an error at a rate depending on latitude (and therefore the direction and distance you have travelled). Direction actually tracked depends on the error, and that error is changing on a daily cycle (actually a 23-hour-56-minute cycle!). Therefore the error at a given point on a track depends on how long you took to get there, and so on your speed. This is of course all compounded by transport drift, and is beyond any but a fairly competent mathematician (rather beyond me!) and certainly beyond the retired RAF navigators who write the learning objectives and most of the questions
!If you have any further questions feel free to email me - I was nav instructor at SFT until their fall.
Joined: Dec 2001
Posts: 546
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From: europe
I would guess a spiral,as the aircraft is actually flying a circular course in space, thus causing the gyro to precess, and as it continues its precession, a heading held with reference to the gyro would be a spiral. Direction of the spiral would depend on direction of spin of the gyro, ground speed, and possibly direction of flight.
Joined: Jan 2002
Posts: 100
Likes: 0
From: UK
Nav?
When i told someone i was doing the ATPL's there comment was something on lines of- [quote] Whoever or wherever your God may be, you will need him now![ <hr></blockquote>
[ 01 February 2002: Message edited by: Rowley ]</p>
When i told someone i was doing the ATPL's there comment was something on lines of- [quote] Whoever or wherever your God may be, you will need him now![ <hr></blockquote>
[ 01 February 2002: Message edited by: Rowley ]</p>
