Which way the wind blows
 

Have you ever wondered if headwinds & tailwinds cancel out over a flying lifetime? In years gone by the answer might depend on if you're a the-glass-is-half-full or a the-glass-is-half-empty kind of person. But my latest GPS has an average ground speed function &, if you don't reset it after each flight, it keeps displaying the cumulative average.

After 6 months its reading 80.5 kts for the R22 which is pretty close to the still air speed. So I've decided that yes, the long term average of whizzing along at 120 kts like an R44 some days & counting the fence posts at 40 kts on other days, is in fact 80 kts.

Hmmm... interesting.:confused:

I suspect if you're in the business of going back and forth (along the same route), you would in fact be trying to maximise the tailwinds and minimise the headwinds for increased efficiency. In this particular example, I would expect the results not to even out (especially if you're doing your job properly).

In the miltary, when conducting TOT or Elapsed Time navs, the idea was to try and even out the effects of the wind by slowing down when there was a tailwind and vice-versa. This would tend align more with your theory and I would imagine that the results would be similar.

I would therefore conclude that the type of flying you're engaged in would have a marked bearing on the actual result. Unfortunately, I haven't kept any records to back this up with.:(

Cheers,

P68:D

Just had another thought...

I tend to hover into wind whenever I get the chance and I would like to think that most of my take-offs and landings likewise were into wind.

This would skew the results somewhat.:bored:

P68:D

I must be bored today...

Just so long as you don't adopt the mistaken impression that on any given flight, the headwind out will be cancelled out by the tailwind home!

No the winds never really cancel out. Since wind direction is really random, the "average wind" is from 90 degrees abeam. Take out your little wizz wheel and see that a wind from the side still slows you down!
Any wind is a bad wind, in the end.

My end has bad wind too....sometimes :O

Mmm.. well, in the R22, whenever i am flying cross country, with a headwind, i get a terrible groundspeed (eg 80 kts indicated and only 50 kts groundspeed)

so... i think "at least on the way home i will have a groundspeed of 110kts"

but it never seems to work that way. i've no idea why.

I've noticed, whenever I cycle to work, that the wind's against me on both directions. Rather bizarrely, it's uphill in both directions, too.

I've never figured that out.

It's because the detrimental effect (headwind) is experienced for longer than the beneficial effect of the tailwind. As soon as a wind gets involved, you need more fuel than you would in still air.

Example: Every day, you fly a Bell 206 from Rainbow Lake (where there is no rainbow and no lake!) in N Alberta to Shekhili compressor station, at which there is no fuel. The distance is 50 nm each way and cruise speed 100 kts. Fuel consumption is 29 US gals per hour. On a nil-wind day, therefore, it should be half an hour each way but, with 20-knot tailwinds outbound, you get there in only 25 minutes. The journey back, on the other hand, takes 37.5 minutes, which is 62.5 minutes total. This may not sound much, but with 60-knot winds, you would be flying for 35 minutes longer than expected, and the figures get worse with longer stage lengths, etc. so watch that fuel load! The PNR will always tend towards the departure point, meaning that distance to PNR is greatest with zero wind, and reduces in windy conditions, regardless of direction.

Phil

Or, to put it another way, you fly a 100 nm route at 100 kts in nil wind and it takes you one hour there and one hour back; total time two hours. Then you fly the same route with a 50 kt headwind and it takes you two hours to get there. Immediately you can see that the head wind has slowed down the total flight time and no amount of tail wind will regain it.

All good points so the question we have is this.

Are we looking at this issue purely from a theoretical point of view (which the last couple of posts clearly are) or do we throw in the practical application of what we know and take into account the fact that we try to nullify the effects of headwinds and maximise our exposure to the more favaourable tailwinds?

Again, I stress this would depend on what kind of work you do.

P68:D

I'll have to agree with P68 "it depends on the kind of work you do" I sincerly hope that no tail wind cancels out my head wind or myself!!:\

And on another theoretical note, why is it that we as pilots enjoy tail winds. I became a pilot because i enjoy flying. and a tailwind reduces the flying that i get to do. :hmm: However is it that we are slaves to efficiency, eg. I'm not going to fly slower than the best required speed for the sake of a few more hours in the long run.
Vote 1 for headwinds:ok:

ascj

ascj,

I suppose the avoidance or otherwise of headwinds has to do with where you are in regard to your career.

I've noticed more often than not that pilots are of two varieties (again I stress generally but not always). Those that will fly as much as possible for little renumeration (in order to get those precious hours) and those that try to fly as little as possible for maximum renumeration (in order to well... do nothing really). However we are getting off track here.

Getting back to the original subject matter, the issue of headwinds vs tailwinds depends also on whether you're looking at it from a time perspective or a distance covered perspective. The point was made earlier that if the same distances were covered using the same wind (both in a headwind and tailwind sense), the time spent in the headwind would be greater and one's average speed would be less. The distance spent experiencing either a headwind or tailwind would be be the same however (not withstanding takeoff and landing etc).

Who would have thought this topic so involved?:confused:

P68:D

the original question was neither of time or distance, it was of average speed, as in 212man's example 2hr at 50 vs 1/2 hr at 200, avg SPEED is still 100 kts.

fuel management and times enroute are the big issues that we have to deal with, avg. speed is a fall-out , and as stated, should not be used for other purposes

no ??

Tail winds suck, faster trip, less flight time, less pay, give me a headwind anyday:)

There are some on this thread who need to get out more. May I recommend beer and girls?

My point exactly, more headwind, more money, more beer and girls

I take it flying backwards with prevailing headwinds wouldn't improve the ratio much either......

407 the average speed is surely 80 kts. :confused:
Speed being distance over time. 200nm for the round trip, 2 and half hours for the whole trip
200nm / 2.5 hours
average speed is 80kts.
yes i need to get out more, but i can't find the keys :D

VeeAny, quite sharp for a friday :)