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What is more efficient - to ride the wave or keep an accurate altitude?

Well, I suppose one could fly parallel to the swell on the updraft side, like gliders do, but that was some 20degrees off my desired track,
Perhaps a combination doing s-turns slowing down and turning parallel for a while in the updraft then turning straight downhill into the downdraft to the next wave then again crosswind for the updraft and so on would be the optimal path.

Good luck getting that approved on an IFR flightplan in class A in Palma TMA while crossing the departure paths of Ibiza and Palma airports…

Edited to reflect a truer representation…

Last Edited by Antonio at 07 Nov 13:27
Antonio
LESB, Spain

Antonio wrote:

I estimate I used 25% more fuel due to this stupid precise level concept

How that compares to an alternative routing? (assuming you know you will hit a wave on direct routing)

Paris/Essex, France/UK, United Kingdom

Here is a better example about that with a strong wave when flying near Albenga towards Mallorca in a W-NW wind which basically killed our climb performance…then just as I was about to request a descent, the downdraft relented…
You can see a 700ft increase in GPS altitude as I was flying towards higher SLP while sort-of maintaining FL180.
The GS decrease at around 02:30 is due to a heading change into wind

The sudden GS decrease at about 00:37 is due to a heading change into the wind, the further continued decrease is due to the wave downdraft. I got down to Vy before it relented. In this occasion I did allow myself bigger altitude excursions without complaints from ATC. I did request a stop climb at FL180 from my initial planned FL200. I dont think I would have been able to achieve it.

Last Edited by Antonio at 05 Nov 19:16
Antonio
LESB, Spain

Well , in the above trace you can see our average GPS altitude decreasing by about 70ft as we travel towards lower SLP while aiming to maintain FL100, but this is not a very extreme case…surely I can find a better one

Antonio
LESB, Spain

This thread reminds me of this one.

Administrator
Shoreham EGKA, United Kingdom

Perfect example on how to ride a wave in the most inefficient manner:

Even worse factoring the 50+kts direct xwind and straight track flown

Last Edited by Antonio at 05 Nov 18:21
Antonio
LESB, Spain

I’ll give it a go next time…I estimate I used 25% more fuel due to this stupid precise level concept…problem isI was causing interference with LEIB departures all along, which they can maange more easily with a single altiude (hence ATC’s insiting that we should be precise) . A couplt of departing commercial traffics got stop climbs 1000ft below me for a few minutes until clear. Surely block altitudes make that job more difficult, especially if they are not used to it

Antonio
LESB, Spain

You could request a level block, e.g. FL90 – FL110. We do it all the time for airwork, military formations also often request block levels.

EDFE, EDFZ, KMYF, Germany

The basic rule in gliding (which would be applicable to fuel efficiency) is slow down in lift, speed up in sink.

If you try to maintain altitude while crossing wave you would be doing the opposite – speeding up in lift (thus shortening your time in the lift, where you’re having energy added to your plane for free) and spending more time in the sink by trying to maintain altitude (slowing down, and having energy robbed from you for a longer time period). Just maintaining your speed will be better than speeding up in lift and slowing in sink.

Hypothetical case: 500fpm average up for 2nm, 500fpm average down for 2nm, a Cessna 172 which climbs 500fpm at 75 knots and cruises at 105.

In the up parts, the plane will get to around 120 knots by maintaining power and altitude, and will be in the upflowing air for 1 minute.
In the down parts, the plane will have to slow to 75 and use full power, and will spend 1.6 minutes doing that.
The total time spent to fly the 4nm will be 2.6 minutes.

If the plane simply maintains a cruise of 105kt and rides the wave, it’ll take just under 2.3 minutes to travel those 4nm and never had to use full power.

Andreas IOM

You should definitely follow the flow. Actually, you should exaggerate it, by pitching up in updraughts and pitch down in downdraughts. That way you will maximise time spent in upgoing air and vice versa. That is what glider pilots do in order to win competitions. It has a name, dolphin flying. Of course, this is neither comfortable nor safe or legal in many circumstances, but definitely efficient.

Last Edited by huv at 05 Nov 11:16
huv
EKRK, Denmark
28 Posts
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