Flying below sea level

The ramblings of our community of aviators.

Moderators: Rick, Lance Murray

Post Reply
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
Posts: 4592
Joined: Mon Aug 30, 2010 12:40 pm
First Name: Rich
Aircraft Type: DA40
Aircraft Registration: N40XE
Airports: S39 Prineville OR
Has thanked: 145 times
Been thanked: 1180 times

Flying below sea level

Post by Rich »

... in Density Altitude terms, of course. Most of us have done this. It doesn't have to be unreasonably cold for a low-level airport to be minus one or two thousand feet DA. (Even my home airport (at 3250 ft.) reaches sea level on cold days, such as winter '16/'17 had.) It's not cold alone, as cold temperatures seem to be accompanied by high pressure (we saw 30.60+ for days in a row late last fall all over the Northwest). And assuming the fuel in the tank(s) were also allowed to chill down, it's also more dense, so a given GPH is pushing more lbs/hr into the engine.

We revel in the really great performance and so forth. But in the spirit of obsessing over everything I ponder whether one might not over-stress the engine at such times. Presumably there are safety margins built into the engine, prop, etc. But how far below zero ft. DA do you suppose. It must be a lot. I figure there are days in Fairbanks where we're talking minus 7000 ft., delivering on the order of 20% more takeoff power than "standard". Folks fly a heck of a lot in these conditions.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
User avatar
CFIDave
5 Diamonds Member
5 Diamonds Member
Posts: 2678
Joined: Wed Nov 07, 2012 3:40 pm
First Name: Dave
Aircraft Type: OTHER
Aircraft Registration: N333GX
Airports: KJYO Leesburg VA
Has thanked: 231 times
Been thanked: 1473 times

Re: Flying below sea level

Post by CFIDave »

You can fly and land below sea level for real in Israel; here's a DA62 doing it:

https://www.youtube.com/watch?v=EmR4ALqFveQ

Makes you wonder if the Austro Engine software engineers considered this when programming the FADEC...

(At the opposite extreme, I've heard that landing at Leadville, CO at 10,000 feet is challenging because the engine FADEC is programmed to not go below 30-40% power at that altitude -- despite the throttle being brought back to idle -- to prevent diesel engine "combustion extinction.")
Epic Aircraft E1000 GX
Former DA40XLS, DA42-VI, and DA62 owner
ATP, CFI, CFI-I, MEI
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
Posts: 4592
Joined: Mon Aug 30, 2010 12:40 pm
First Name: Rich
Aircraft Type: DA40
Aircraft Registration: N40XE
Airports: S39 Prineville OR
Has thanked: 145 times
Been thanked: 1180 times

Re: Flying below sea level

Post by Rich »

CFIDave wrote:At the opposite extreme, I've heard that landing at Leadville, CO at 10,000 feet is challenging because the Austro engine FADEC is programmed to not go below 30-40% power at that altitude -- despite the throttle being brought back to idle -- to prevent diesel engine "combustion extinction."
That does seem challenging, dragging out your landing distance big time. The runway isn't all that long given its high elevation. DA's beyond 12,000 ft. aren't uncommon.

And taxiing with all that power? :shock:

What about if you actually land there and shut down? Is there a problem starting the engine?

I kind of don't get it. There's plenty of road diesel traffic and heavy equipment operation in the area and, for that matter, even higher elevations.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
User avatar
neema
4 Diamonds Member
4 Diamonds Member
Posts: 285
Joined: Fri Dec 05, 2014 5:43 am
First Name: Neema
Aircraft Type: DA62
Aircraft Registration: N617DC
Airports: KFAT
Has thanked: 40 times
Been thanked: 97 times

Re: Flying below sea level

Post by neema »

CFIDave wrote:You can fly and land below sea level for real in Israel; here's a DA62 doing it:

https://www.youtube.com/watch?v=EmR4ALqFveQ

Makes you wonder if the Austro Engine software engineers considered this when programming the FADEC...

(At the opposite extreme, I've heard that landing at Leadville, CO at 10,000 feet is challenging because the engine FADEC is programmed to not go below 30-40% power at that altitude -- despite the throttle being brought back to idle -- to prevent diesel engine "combustion extinction.")
I've been meaning to try Leadville. Curious to see if the engines can come down enough in power enough to make it possible.

I'd hope the ECUs can at least set the props to max fine pitch to minimize forward thrust. RPM may get a little high.
jb642DA
4 Diamonds Member
4 Diamonds Member
Posts: 313
Joined: Thu Feb 16, 2017 5:16 pm
First Name: John
Aircraft Type: OTHER
Aircraft Registration: N2691Y
Airports: KPTK KDTW
Has thanked: 51 times
Been thanked: 143 times

Re: Flying below sea level

Post by jb642DA »

CFIDave wrote:You can fly and land below sea level for real in Israel; here's a DA62 doing it:

https://www.youtube.com/watch?v=EmR4ALqFveQ

Amsterdam Schiphol (EHAM) too, 11 feet "below" MSL! - Just flew back from there today.
Looking!
1980 414A - N2691Y (sold)
DA62 - N100DA 62.078 (sold)
DA42TDi - N742SA 42.AC112 (sold)
User avatar
RMarkSampson
4 Diamonds Member
4 Diamonds Member
Posts: 237
Joined: Fri Sep 05, 2014 1:24 am
First Name: Mark
Aircraft Type: DA20-C1
Aircraft Registration: N966CT
Airports: KPCM
Has thanked: 20 times
Been thanked: 45 times

Re: Flying below sea level

Post by RMarkSampson »

Rich,
Per the engine impacts - if a wintertime high pressure system parks over you, you are right Density Altitude (DA) could be a minus 1,500 - a 3K difference in DA from what I see in summer. So LOP flying might require you to climb higher in winter vice what you can do in summer. It was cold the other day and my altimeter setting was around 30.40. I was not being successful in setting my engine controls to LOP at the same altitudes that I easily do in summer. Vice climbing higher, I just kept it ROP.
Post Reply