Headwind vs higher altitude question for Bravo Owners

[JohnB]

Ok this is only a question for Turbo/ Bravo owners. I have noticed that our Bravos are faster and much more efficient at altitude, and its very easy when you have a tailwind to select a higher altitude based on tailwind, but what about a headwind? So how much additional headwind would you take on to get the efficiency of going higher in our Bravos? Is there a simple formula you use to decide? Here's an example. Assuming terrain is not at all a factor, and you've got plenty of oxygen on board, and 0 degrees C at 10k with standard temperature changes with altitude. In the direction you're flying, your winds aloft are:

• 7k - wind calm
• 9k - 5 knot headwind
• 11k - 10 knot headwind
• 13k - 15 knot headwind
• 15k - 20 knot headwind
• 17k - 25 knot headwind (and same increasing by 5 knots per 2k feet all the way up to 25k)

What altitude would you choose for best speed and fuel economy? 7k to maximize wind advantage or? Again this is only a question for Bravo/ Turbocharged engine folks. Thanks!

 

[carqwik]

An easier way to think about the problem is by using TAS at 10k, 15k, and 20k feet...which in my plane is ~175, 188, and 198 kts respectively at normal cruise of 30/2400.  So subtract the headwind at each altitude from TAS and determine which altitude gives you fastest ground speed...that is the answer.  Fuel burn is the same at each altitude for a  given power setting.  Of course, trip length also factors into the equation since it takes a long time to get to FL200 at cruise climb.

[JohnB]

Nice formula carqwik, interesting and simple, thanks!  Did you use temperature or demonstrated speeds at your power settings at altitude to calculate your expected TAS at altitude?

[FlyDave]

fltplan.com will show you performance (TAS/Winds Aloft/Fuel burn) for a range of about 10,000' or 12,000'. It's very accurate - usually within 2 gallons on a 2.5-3 hour flight.

I have 2 profiles on fltplan.com - on for economy (26" and 2400 RPM, 15.5+ gph) and one for high cruise (29" and 2400 RPM, 18.5+ gph). They are both quite accurate if I don't get vectored/delayed a lot. My profiles increase FF with altitude as the air is thinner and you need a little more cooling as you go higher.

[Awful_Charlie]

I put a spreadsheet up in post http://mooneyspace.com/topic/10523-mike-busch-webinar-on which I often use - the figures come from the POH and it's adapted for EU forecast levels, but should be easily changed. I also keep a 1 page on my kneeboard with KTAS/KIAS/FF as well as critical speeds, so if needed it's a bit less painful to re-calculate in flight

[Z W]

As a general rule of thumb, keeping your power settings the same, you will gain 2 KTAS per thousand feet you climb in a turbo'd plane.  

 

So, take the # of feet in thousands you are thinking of climbing, x 2, and you know how much airspeed you will gain going up.  Compare that to the forecast winds aloft to decide if it's worth climbing higher.

 

Example:  My plane does 170 KTAS at 10k feet.  It does about 186 KTAS at FL180.  That's a gain of 16 KTAS.  If the winds at FL180 are more than 16 KTAS worse, I don't go up.

 

Also, because of the time spent climbing and descending, and the need to put me and all the passengers on oxygen, it has to be significantly better up high before I will go up.  I won't climb 8k feet and use up my O2 for a 5 knot gain in groundspeed.

 

As a practical matter, above 10k, it seems like the winds almost always gain strength faster than I gain KTAS.  I almost never climb into a strengthening headwind, and only go up for a tailwind.  But I really love those tailwind days...

[Danb]

Charlie. I'v reviewed and printed your matrix..which I plan on utilizing.it was nicely done and makes sense ...I believe that if one just modifies it slightly for their airplane which I did its a time saver and very useful..Nice.....BTW you need to get a life.LOL   Dan  Bravo power~!!!

[AndyFromCB]

Don't forget that it's not just about speed, either. I go high sometimes, even if actually slower for bumps, safety over terrain and to stay out of the soup.

[aaronk25]

Ok....I know I'm not supposed to chime in cause I don't yet have a turbo, but I routinely fly my J upto 18k and will take a slight headwind and fly at 13-15k instead of 7k for the same reasons as stated above.....smoother....less traffic....and less chance of surprise traffic showing up on atc radar "12'oclock 1 mile". Happens a lot at 5k.

In a turbo bird I wouldn't fly less than 10k under most circumstances unless there was a 30kts difference. For me even if I could only net 10kts more it would be service ceiling cruse for 2 hours or more.....

[M016576]

Ok....I know I'm not supposed to chime in cause I don't yet have a turbo, but I routinely fly my J upto 18k and will take a slight headwind and fly at 13-15k instead of 7k for the same reasons as stated above.....smoother....less traffic....and less chance of surprise traffic showing up on atc radar "12'oclock 1 mile". Happens a lot at 5k.

In a turbo bird I wouldn't fly less than 10k under most circumstances unless there was a 30kts difference. For me even if I could only net 10kts more it would be service ceiling cruse for 2 hours or more.....

You know what they say about your favorite fishing hole.... Don't let the word get out or you'll see everyone and their mother there

[Danb]

Even in my Bravo I seem to get hooked on some numbers i.e.. altitudes ..I like to fly as high as I can while keeping my other half happy especially on legs over 3.5 hours, seems like she turns into some kind of fidgety monster after 3 hours, she can fly without problems up to about 13000 feet, I use o2 at 8000 we do use an oximeter. So on say 2-3 trips no problem can do 15000 which my Bravo likes, longer trips 13000 or a little lower, but if wx or winds matter all bets are off I just turn her off, give her  an ipad to play with turn off her headset and fly..thats after the 3+ hour mark, so all this figuring I do to find the most efficient altitude goes out the window on lots of occasions..maybe I'm the only one who has  a monster as co-pilot???

[JohnB]

Hugely helpful guys, and wow Charlie!! Amazing spreadsheet! Ill be using it, and man.. you must have had a LOT of time on your hands but thanks!!! Appreciated!! Havent used fltplan.com much, but I now see how it could be helpful to calculate TAS then plug that into a foreflight app then voila. Or I could use Charlies amazing spreadsheet!

 

Danb, my other half had an issue about going higher, and doesn't like turbulence. So after explaining that higher is actually safer, and usually smoother, particularly over mountains,  I flew my outbound trip at 8k around lots of bumpy clouds, and a return leg at 17k on oxygen, smooth as a baby. I also gave her her own pulse ox she could check anytime and constantly if she wished and allowed her to adjust her o2 flow if she wished. She was much better with that when she was keeping her own sat 98%+, and i was thoroughly enjoying the 240+ knot ground speeds, compared with 150 knots going out with same power settings. AND I burned less gas on a longer return route distance. At least my Bravo likes it above 10k! Hence my question about headwinds, thanks all.. this is really useful stuff!

[N201MKTurbo]

Don't forget that the only planes in the high teens are turbo piston planes. A rare bunch, you own the sky and can get direct to anywhere!

[Awful_Charlie]

Charlie. I'v reviewed and printed your matrix..which I plan on utilizing.it was nicely done and makes sense ...I believe that if one just modifies it slightly for their airplane which I did its a time saver and very useful..Nice.....BTW you need to get a life.LOL   Dan  Bravo power~!!!

Well done Dan - that was really the idea - start with something and then modify it to get exactly what you want. I'm hoping I get a life in the next one   That matrix isn't ideal for printing, as it's intended as a calculator - the knee board sheet I hinted at is attached - it is highly individual (things like the wing gauge calibrations) and uses a lot of space for unt conversions that you probably don't want, but I like to have all the POH figures for the various speeds at different weights to hand, and having book performance converted to KIAS is handy to make sure you're getting what you were promised!

 

Don't forget that it's not just about speed, either. I go high sometimes, even if actually slower for bumps, safety over terrain and to stay out of the soup.

I agree totally. I tend to get the MSA/MEA, then the optimum altitude (hopefully higher than those!), and and idea of the trade-offs. If en-route it gets uncomfortable/boring/continuous ice/whatever, can make an informed guess as to which way and how much to change the level

 

Hugely helpful guys, and wow Charlie!! Amazing spreadsheet! Ill be using it, and man.. you must have had a LOT of time on your hands but thanks!!! Appreciated!! Havent used fltplan.com much, but I now see how it could be helpful to calculate TAS then plug that into a foreflight app then voila. Or I could use Charlies amazing spreadsheet!

 

Danb, my other half had an issue about going higher, and doesn't like turbulence. So after explaining that higher is actually safer, and usually smoother, particularly over mountains,  I flew my outbound trip at 8k around lots of bumpy clouds, and a return leg at 17k on oxygen, smooth as a baby. I also gave her her own pulse ox she could check anytime and constantly if she wished and allowed her to adjust her o2 flow if she wished. She was much better with that when she was keeping her own sat 98%+, and i was thoroughly enjoying the 240+ knot ground speeds, compared with 150 knots going out with same power settings. AND I burned less gas on a longer return route distance. At least my Bravo likes it above 10k! Hence my question about headwinds, thanks all.. this is really useful stuff!

It took a few evenings, but at the time I couldn't find anything with a similar functionality. Some tools are starting to appear which do the job better, as in they consider the GFS mnodel along the whole route, but so far I've not found one of these that copes with different power setting models....

 

Don't forget that the only planes in the high teens are turbo piston planes. A rare bunch, you own the sky and can get direct to anywhere!

Particularly more so in the low 200's - some NA stuff (like Ovs and TB20's, and Aaron) are going up to FL200, and the turboprop stuff is probably going as high as they're allowed (so 250-260 seems quite common). Somewhere in the 200-240 is great and directs are normally only limited by pilot and controller imagination!

CruisePerf25k-b.zip

[aaronk25]

Don't forget that the only planes in the high teens are turbo piston planes. A rare bunch, you own the sky and can get direct to anywhere!

Don't for get about me.....I drag my NA j around at 17k if I have a tail wind....crossed the gulf at 19k....don't run me over!

[N201MKTurbo]

it's a big sky out there. I think you are safe.

[Piloto]

If you want to find at what altitudes turbo Mooneys fly in the real world Just click here

http://flightaware.com/live/aircrafttype/M20T

 

For non turbo Mooneys click here

http://flightaware.com/live/aircrafttype/M20P

 

For Cirrus SR22 click here

http://flightaware.com/live/aircrafttype/SR22

 

Impressive! Looks like Cirrus pilots are very active

 

José

[carusoam]

Cirrus. 160 kts

Mooney 190 kts

I'll go with a Mooney, again...

-a-

[Piloto]

Cirrus. 160 kts

Mooney 190 kts

I'll go with a Mooney, again...

-a-

 

Me too. I personally don't like plastic planes, specially flying here in Florida in the Mecca of lightning. But the reality is that Cirrus buyers are not concern about speed but maybe style. Would you by a car that only has one entry door?. When you look at a Cirrus it reasembles many of the features found in modern cars. Aerodynamic lines, a car center console and others. And the parachute that gives the buyer the false sense of safety. No retractable landing gear to worry about. 

 

The Mooney looks like a real airplane but for some buyers may look too complex to fly. Yes the Mooney has a retractable gear but for the Cirrus prospective buyer there is no difference from a Mooney on the ground or inflight, not even when landing, both have the gear extended. The only time you see how clean the Mooney looks is when is on jacks.

 

If Mooney wants to compete with Cirrus it has to come with a real differentiator. Noise reduction is a start, a fifth seat, retractable shades like the airlines and others.

 

Why would the market share be better this time if they are going to be selling the same model for $200K more? After all Cirrus is owned by the Chinese.

 

José