REL Posted January 21, 2011 Posted January 21, 2011 (edited) Somewhere in the manual : 1. "Descend at a rate of -300 feet for every mile traveled. " 2. "The VVI displays rate of climb or decent in increments of feet per minute." The Question : How can I translate Info 1 to the VVI Indication value (Info 2) ? I guess I'm trying to find a way to convert the "every mile traveled" to "feet per minute". Edited January 21, 2011 by REL
skypirate Posted January 21, 2011 Posted January 21, 2011 Somewhere in the manual : 1. "Descend at a rate of -300 feet for every mile traveled. " Perhaps the followin article might give you some light on the matter: http://en.wikipedia.org/wiki/Rule_of_three_%28aviation%29 Though being a fighter pilot you should not be so concerned about your eardrumms ;) [sIGPIC][/sIGPIC]Regards!
Flamin_Squirrel Posted January 21, 2011 Posted January 21, 2011 (edited) A quick approximation is to divide your airspeed by 3 then multiply by 10 to get vertical speed. i.e 130 kts divided by 3 is a little over 40, say 43, multiply by 10 or, to keep it simple, just add a zero - 430 fpm. This also equates to approximately 3 degrees meaning, place the velocity vector in the hud somewhere around half way between the 0 and -5 degree pitch bars and you'll get the same result. Using either method is also very useful for judging approach, as most are done on a -3 degree glide slope. Edited January 21, 2011 by Flamin_Squirrel
REL Posted January 21, 2011 Author Posted January 21, 2011 A quick approximation is to divide your airspeed by 3 then multiply by 10 to get vertical speed. i.e 130 kts divided by 3 is a little over 40, say 43, multiply by 10 or, to keep it simple, just add a zero - 430 fpm. This also equates to approximately 3 degrees meaning, place the velocity vector in the hud somewhere around half way between the 0 and -5 degree pitch bars and you'll get the same result. Using either method is also very useful for judging approach, as most are done on a -3 degree glide slope. Thanks Flamin_Squirrel
Dynamo Posted January 21, 2011 Posted January 21, 2011 A quick approximation is to divide your airspeed by 3 then multiply by 10 to get vertical speed. i.e 130 kts divided by 3 is a little over 40, say 43, multiply by 10 or, to keep it simple, just add a zero - 430 fpm. This also equates to approximately 3 degrees meaning, place the velocity vector in the hud somewhere around half way between the 0 and -5 degree pitch bars and you'll get the same result. Using either method is also very useful for judging approach, as most are done on a -3 degree glide slope. Squirrel, is your method just a way of approximating a 3 degree glideslope, like these? http://www.scgvacc.net/forum/index.php?showtopic=359 REL, in the manual, page 489: descend to the TACAN station location at a rate of approximately 1,200 to 1,500 ft/min on the ―VVI‖ indicator -300 feet for every mile traveled and maintain 200 – 250 KIAS. So in your case, maintain a speed of 200-250 KIAS, and maintain -1200 to -1500 fpm.
Flamin_Squirrel Posted January 21, 2011 Posted January 21, 2011 Squirrel, is your method just a way of approximating a 3 degree glideslope, like these? http://www.scgvacc.net/forum/index.php?showtopic=359 REL, in the manual, page 489: descend to the TACAN station location at a rate of approximately 1,200 to 1,500 ft/min on the ―VVI‖ indicator -300 feet for every mile traveled and maintain 200 – 250 KIAS. So in your case, maintain a speed of 200-250 KIAS, and maintain -1200 to -1500 fpm. Yep.
effte Posted January 21, 2011 Posted January 21, 2011 Ground speed times ten divided by two is easy to calculate on the fly for a three degree glideslope. 160 knots gives 1600/2 = 800. The "true" figure is 850 fpm, so it's close enough for government work. You're going for 320/60 fpm per knot of groundspeed (320 feet per mile, GS/60 miles per minute). Times five, or 10/2 as per above, is only a few percent off. Ignoring the conversion to ground speed and using airspeed instead is usually very acceptable. At 5000 feet, the difference is only around eight percent (standard atmosphere). At A-10 approach speeds, you can also ignore all but extreme head/tailwinds. 430 fpm isn't quite right for 130 knots. Back of an envelope gives me a 1.9 degree glide? Typo on the factor three? ----- Introduction to UTM/MGRS - Trying to get your head around what trim is, how it works and how to use it? - DCS helos vs the real world.
Flamin_Squirrel Posted January 22, 2011 Posted January 22, 2011 Ground speed times ten divided by two is easy to calculate on the fly for a three degree glideslope. 160 knots gives 1600/2 = 800. The "true" figure is 850 fpm, so it's close enough for government work. You're going for 320/60 fpm per knot of groundspeed (320 feet per mile, GS/60 miles per minute). Times five, or 10/2 as per above, is only a few percent off. Ignoring the conversion to ground speed and using airspeed instead is usually very acceptable. At 5000 feet, the difference is only around eight percent (standard atmosphere). At A-10 approach speeds, you can also ignore all but extreme head/tailwinds. 430 fpm isn't quite right for 130 knots. Back of an envelope gives me a 1.9 degree glide? Typo on the factor three? Yep you're right, it should be 2, my bad.
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