Journal from Qi and friends
Planes and Climate, on 150 Hours Logged


Private Pilot, ASEL
157.2 hours


Qi Linzhi

Written in

Winter 2021

I’m a plane nerd. Planes were a childhood fascination that I never got over with, and then I was lucky enough to be introduced to general aviation. Aviation’s hard dependency on fossil fuel makes it harmful to the planet.

As a forcing function to reflect on the environmental impact of my activities, I’m making myself jot down some notes after every 100 hours. Hopefully for other GA pilots and flight enthusiasts, my struggle for reconciliation is relatable.

Short run: carbon offsetting

In the last entry, I wrote about the logistics of the (mostly psychological) remedy of carbon offsetting from theoretical fuel consumption. The cost of offsetting Avgas remains at 8 cents per gallon but went from 1.7% to 1.5% of fuel cost because of the record oil price.

The arithmetics got a bit trickier. Since my primary training, I’ve been flying a wider variety of aircraft makes with different engines types:

Lycoming POHs

O/IO-360, pp. 53, 56

O-320, pp. 32

O/IO-540, pp. 61

  • Piper Archer 100i/LX: Lycoming IO-360-B4A at 14.5 max gph
  • Cessna 172M: Lycoming O-320-E2D at 14.0 max gph
  • Cessna 172R: Lycoming IO-360-L2A derated to 160 hp at 12.7 max gph
  • Cessna 172SP: Lycoming IO-360-L2A at 14.5 max gph
  • Cessna 182T: Lycoming O-540-L3C5D at 24.5 max gph

Starting hour 129.6, I added a checklist item after engine shutdown to copy the reading of the fuel totalizer, if available, to my logbook. It’s also a great awareness moment to nudge me and my passengers about the carbon footprint of each trip.

In the 27.6 flight hours since, I’ve logged consumption of 256.5 gallons of 100LL from 16 flights, which would have been estimated at 444.2 gallons based on max fuel flow of respective engine types. Subsequently, I’ve adjusted my carbon offsetting amount to 3x the actual fuel consumption from 2x the theoretical max.

GA vs. short-haul commercial flights

According to Google Flights, a trip from Hollywood Burbank (KBUR) to San Francisco International (KSFO) emits 216 pounds per seat on a Boeing 737-700 (operated by 5 times a day by Southwest) or 419 pounds of CO₂ per seat on a CRJ-200 (operated by 3 times a day by United).

I flew a Cessna 172 on a VFR trip from KBUR to San Carlos (KSQL), 10 miles south of SFO. The day was overcast with headwind over 10 knots, and I had to maneuver to dodge scattered clouds and localizer courses. With best power mixture during cruise, I logged 26.9 gallons of fuel burn, or 123 lbs of CO₂ per seat — about a quarter to a half of that for airlines, but the comparison has a couple of caveats.

Airliners have to follow assigned routes, but I could just VFR direct. If I were instrument-qualified and accepted IFR services on an overcast day, ATC would probably send me on a farther zig-zag path than an airliner due to handling priority and my service ceiling.

Another concern is passenger load factors. The Cessna 172 has four seats but hardly the useful load to take three friends if there are any who want to come along. So far, I’ve logged 25 unique passengers or 59 passenger-trips as PIC. The math adds up to an average load factor of 48% excluding my own occupancy or 63% including, while airlines usually operate in the high 80s to 90s. All this means the effective trip carbon footprints comparable to short-haul commercial flights in modern jets.

Of course, another catch is most GA trips are less necessary and have more viable ground transportation alternatives.

Long run: decarbonizing

My grim outlook of electric planes hasn’t changed since the last journey entry.

Airbus Announcement


Airbus announced in September three concept aircraft powered by hydrogen cells that hoped to see commercial flights in 15 years, a “challenging and highly ambitious” goal. When asked about the hydrogen planes in relation to the E-Fan electric aircraft project canceled in 2017 in very rehearsed Q&A, Airbus CTO Grazia Vittadini said, “all our learnings on this demonstrators will flow seamlessly, of course, into any new consideration considering hydrogen as a key component of a hybrid system.” I sure hope so.

ZeroAvia Press Release

Test 86

So it seems like the future is hydrogen? In April, the world’s first hydrogen fuel cell-powered passenger aircraft, a modified Piper Malibu by ZeroAvia, landed “off-airport” on a field in Bedfordshire, UK. Official AAIB report is still pending, and the almighty Dan Gryder from DTSB does not have jurisdiction over the UK. The test crew survived the crash landing, and the company probably will too, but incidents like this make me wonder how long it would take for the general public to develop the risk appetite to fly in one of these birds.

There’s one thing at least Airbus seems certain about in the press event: “15 years from now. That’s tomorrow in our industry.”