View Full Version : Winds FL410 - FL510 over the Pacific
nomorecatering
9th Apr 2006, 01:03
I was wondering about the usual winds at these levels between YSSY and KLAX and trying to settle an argument. ATPL met notes state that above the tropapause the winds generally die off. Is that true in real life, or is there still a stronger prevailing westerly flow ablove FL410. Also understood is that the tropopause gets higher as you get closer to the equator.
Basis for the discusion is about the Citation CJ3 for trans pacific ops. sector lengths would be right on the range limit. Particualar HNL - LAX. There for the requirement to to find out abot the winds.
Cheers
Capt Fathom
9th Apr 2006, 01:18
Try this website... http://aviationweather.gov/
Menus on the left side of the page should give you what you are after!
gaunty
9th Apr 2006, 01:36
nomorecatering
Hmmm Citation CJ3 for trans pacific ops. its a fantastic aircraft, but I wouldn't have thought it was the optimum aircraft for that role.
Yes above the tropopause the winds generally die off and it does get higher the closer to the equator which is why you get that humungously high CB development compared to the mid and higher latitudes and why the jetstreams are and where they are.
First glance, the bulk of the journey is going to be at mid latitudes which is more likely to get you above it, but mid latitudes are also where the westerlies live and remember Mn is a function of temperature not altitude. We are fortunate that temp decreases with alt. Increasing altitude above the tropopause does not bring any more (or not significant) increases in Mn so we are relying almost totally on, given a reducing TAS, whatever winds there may be to help us with SGR.
And some where or other in the journey, up and back, you are going to have to deal with the ITCZ and what that brings, put island and local weather on top of that and IMHO you are out of room in the tanks.
Eastbound maybe Westbound cant see it.
I'm getting a bit scratchy on this but the CJ3 is going to be routinely operating on tippy toes over these routes and sweating fuel over water is not my idea of routine fun.
nomorecatering
9th Apr 2006, 03:16
More of a brainstorming excercise than serious intent, but then again....who knows. The brief was for a personal, owner flown jet, 1 person, maybe two. Other contenders could be the SJ30-2, heaps of range 2500 nm, 450 kts and FL490 max alt capability. Possibly the Phenom 300 from Embraer, looks beaut but maybe a little short on range.
Now if winglets transformed the 737 next gen, and seems to be the rage these days, how difficult would it be to design a set for the CJ3, coupled with an extra 700 lbs of fuel in the baggage area to bring it up to max TOW. 2 up with max standard fuel you still have 700lbs below max weight. Something along the lines of a Sierra Eagle CJ3.
Yes, why would you go to all that bother when one could merely book a first class seat on the Rat, but life is about what is good and fun, not what makes sense. How else would you explain snow skiing.
Ok, dumb question time....what is Mn? can you elaborate more on that paragraph, not sure i follow what you're saying.
Edited numerous times cause I really suck at spelling.
*Lancer*
9th Apr 2006, 03:19
Can it get to that sort of altitude at that weight?
No airliner can... 747 sticks to the mid-300s.
gaunty
9th Apr 2006, 04:15
nomorecatering
Mn = Mach No. sorry, should have been clearer.
Winglets and certification on a new model nahh thats not going to happen any time soon and in any event there are other penalties for extra fuel and so on.
May I suggest that after a couple of journeys of serial up and down and nail biting the owner will very quickly.
In any event as *Lancer* suggests the probability of tropopause cruise for any part of the journey in those lats is highly improbable.
And the extra weight of fuel and the temps are going to have you down in the 30's for most of the time.
If you haven't yet, go have a look at what DP Davies has to say. It is as relevant today as it was 30 odd years ago.
gaunty
9th Apr 2006, 04:15
nomorecatering
Mn = Mach No. sorry, should have been clearer.
Winglets and certification on a new model nahh thats not going to happen any time soon and in any event there are other penalties for extra fuel and so on.
May I suggest that after a couple of journeys of serial up and down and nail biting the owner will very quickly.
In any event as *Lancer* suggests the probability of tropopause cruise for any part of the journey in those lats is highly improbable.
And the extra weight of fuel and the temps are going to have you down in the 30's for most of the time.
If you haven't yet, go have a look at what DP Davies has to say. It is as relevant today as it was 30 odd years ago.
nomorecatering
9th Apr 2006, 06:31
The P Charts.....well charts drawn up by the marketig dept st Cessna, as on their CJ3 website list that at max TO weight the CJ3 can climb directly to FL450.
TO weght 13,870 lbs
Dist 139 nm
Time 27 mins
Fuel 591 lbs
ISA Temps
Capt Fathom
9th Apr 2006, 07:43
You won't find ISA temps across the Pacific, and climbing up into 'coffin corner' is not for the faint hearted!
I'm sure you well aware of the confidence the marketing people have in the ability of their aeroplanes. What they say however, is often not achievable or not practical in the real world!
The CJ3 is a Citation which performs better than the book numbers.
You can expect FL450 in 22 mins at MCTOW. Above FL400 it'll still be climbing at 1000fpm. Having said that we only visit 430 and 450 when we have to.
I believe cessna states about a 1900nm range plus reserves but 2000nm wouldn't be a problem with a 100nm alternate and reserves.
Hawaii to the west coast of the U.S. would be possible but the return wouldn't. That means a visit to Alaska/Aleutian Islands - Petro - Japan and Palau/Guam - Cairns.
A CJ3 to be delivered shortly is about to make this trip, apparently taking the scenic route on the way to it's new home in the UK.
nomorecatering
9th Apr 2006, 12:42
C525B,
Thanks for your input. Had heared reports that the CJ3 was performing much better than expected. Out of curiosity, what level do you usual use initially, then later on. Do you go lower for the extra TAS?.Would be much interested to hear what TAS/fuel flow you are actually getting. Seems that Cessna/Williams Rolls have done a masterful job on this aircraft.
With 2 up, I read you still have some 700-800 lbs of useful load left before hitting MTOW. Is additional fuel tanks(say in the baggage compartment - or anywhere else) a viable option. That would certainly solve the marginal range problem.
Your comments are keenly awaited.
We climb directly to FL450. The tas up there will start at 405 knots and increase slowly towards 415. Fuel flows are around 790 lbs/hr as opposed to 950 lbs/hr at FL390.
With 2 pilots, max fuel you do still have that 700-800 lbs available but I don't think extra tanks in the baggage compartment would be practical. If you want a 2500nm aircraft I don't think the CJ3 is for you.
bushy
10th Apr 2006, 03:00
It is only in Australia that aircraft will not make book figures. Everywhere else in the world they make book figures, even when they are 30 years old.
I wonder what slows them down when they come here.
halfhardt-6
10th Apr 2006, 03:52
Using a CJ3 for regular trans-pacific ops! I suggest you use the money that was to be spent on the a/c to remove the rocks in your head.
Seriously though, tell your friend/boss/investor to think about another machine. I've spent many an hour in a similarly sizes biz-jet across various countries and oceans and it doesn't take long to start wishing you were in something bigger and more capable or in the nice part of an airliner.
This is especially true when encountering the ascociated weather near and around the equator.
But good luck to you if you can sell him/her one.
nomorecatering
10th Apr 2006, 04:59
A Biz Jet is a big improvement over what my friend currently uses, he's based in CA and has flown all over the world, first in a Mooney, now has an Aerostar 600. Been accross the Atlantic a dozen or so times, twice accross the Pacific to Oz. Now looking for something bigger, faster, more comfy. Something he can fly himself. I was suggesting the CJ3 or SJ30.
Rocks in his head, probably. But thats what he likes to do. Ex military fast jet (USAF) and now National Guard. So well experianced and qualified. His bother sails round the world solo yaught races.....now thats what I call having rocks in your head. why do they do it?................cause they can.
Oh, hes just bought a new toy, an L39 Albatros. next time i get myself over there hes gonna give me a ride....wooo hooo.
*Lancer*
10th Apr 2006, 08:54
Just get him a set of really big drop tanks! ;)