kallend 2,027 #1 January 16, 2004 You are a DZO and pilot at a small Cessna DZ. You have to drop off some equipment for repair and then return home. You will take the plane. The repair shop is due east of your DZ. Your plane's cruise airspeed is 100kt. The wind forecasts for the next few days are: Day1. Wind calm Day 2. Outbound: headwind of 30kt, return: tailwind of 35kt Day 3. Wind from due north at 30kt for both out and return legs. Your time is valuable. Which day would you go if you want the quickest round trip? Which day is the slowest?... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Phillbo 11 #2 January 16, 2004 2 for quickest.. you get an overall 5knt increase in speed for half the trip. Quote Share this post Link to post Share on other sites
NZL60 0 #3 January 16, 2004 I'm gonna go with 2 for the quickest and 3 for the slowest Who said Kiwis can't fly? Quote Share this post Link to post Share on other sites
rehmwa 2 #4 January 16, 2004 It's 1. I'll show the relative scale of time in a sec. Fix that 1 is fastest 2 is slowest headwinds suck ... Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants Quote Share this post Link to post Share on other sites
Taylor610 0 #5 January 16, 2004 Definately # 4, BEER THIRTY! Send it UPS and let them worry about having it there by 10 am tomorrow morning. Quote Share this post Link to post Share on other sites
rehmwa 2 #6 January 16, 2004 'd' is the distance flying (it's in some wierd units that allows us to work in a velocity of knots instead of mph or ft/s or m/s - what can you do?) case one: time = d/v (first leg) + d/v (2nd leg) = d/100 + d/100 = 0.02 d case two: same thought = d/(100-30) + d/(100+135) = d(70+135)/(70*135) = 0.0216931 d case three: the velocity in a straight line requires crabbing to the target so v = sqrt(100^2-30^2)) v= sqrt of 9100 or about 95.39 knots so t = d/95.39 + d/95.39 = 0.020966 d like I said, headwinds always suck (or blow depending on which way you are facing) ... Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants Quote Share this post Link to post Share on other sites
freeflygoddess 0 #7 January 16, 2004 QuoteDefinately # 4, BEER THIRTY! Send it UPS and let them worry about having it there by 10 am tomorrow morning. hehehe I concure, but FedEx...and ask for Mike! edit: oh yes and whilst Mike is there picking up your repair stuff and whilst he is dropping it back off, make sure you talk him into bringing his kingair there and stuff...not only will your repairs get fixed but you will also solve the delima of a small Cessna DZ Quote Share this post Link to post Share on other sites
PhillyKev 0 #8 January 16, 2004 Yeah...definitely #2 is slowest. If you just take the average between the headwind and tailwind air speeds, it seems like 2 is faster. Except you're moving through the air. So with the headwind, you're actually travelling a longer distance through the air even though distance over the ground is the same. Since you're travelling further at the slower speed, it skewes the average for the total speed down. Quote Share this post Link to post Share on other sites
NZL60 0 #9 January 16, 2004 hmmm.. I think I see that... I was thinking in terms of what was the fastest overall speed therefore (mistakingly) quickest.. cool prof? Although have to say the UPS option was more appealling.. next time make it some metric quizz and ban quade from the discussion Who said Kiwis can't fly? Quote Share this post Link to post Share on other sites
kallend 2,027 #10 January 16, 2004 QuoteIt's 1. I'll show the relative scale of time in a sec. Fix that 1 is fastest 2 is slowest headwinds suck Absolutely. Lessons: 1. In aviation, you can never win when wind is involved. 2. Averaging speeds is trickier than it looks at first glance.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Taylor610 0 #11 January 16, 2004 You got that right! Quote Share this post Link to post Share on other sites
champu 1 #12 January 16, 2004 Quote'd' is the distance flying (it's in some wierd units that allows us to work in a velocity of knots instead of mph or ft/s or m/s - what can you do?) nautical miles? (~6076ft) IIRC it comes from the arc length of one minute of longitude, whereas a statue mile (5280ft) originally came from "1000 paces" or something asinine like that. Quote Share this post Link to post Share on other sites
happythoughts 0 #13 January 16, 2004 Quote2 for quickest.. you get an overall 5knt increase in speed for half the trip. I'm not an aircraft engineer, but I'm thinking that there is a difference between the way a headwind and a tailwind affect a plane. It's not like a beachball where the wind uniformly hits the surface. Quote Share this post Link to post Share on other sites
AndyMan 7 #14 January 16, 2004 No, it's not that. A plane flies in its own airspace, and doesn't really care which way the air is moving. Here's what it is - obviously a headwind slows down a plane. However what we forget is that by slowing down the plane, the plane has to stay aloft for a longer time to get to its destination. The plane has to stay in the headwind for longer, thus amplifying the affect. A plane flying with a tailwind will get to its destination faster, thus spending less time in the effect of the tailwind. Thus - a headwind of 5 knots affects the plane for a longer period of time then the same tailwind of 5 knots. They do not balance out. _Am__ You put the fun in "funnel" - craichead. Quote Share this post Link to post Share on other sites
Jonno5 0 #15 January 16, 2004 I would go for calm wind....and enjoy the smooth ride. Quote Share this post Link to post Share on other sites
FallRate 0 #16 January 17, 2004 Quote1. In aviation, you can never win when wind is involved. I'll take a tailwind on my one-way trips. FallRate Quote Share this post Link to post Share on other sites
