3
$\begingroup$

In the article here : https://abcnews.go.com/Health/Healthday/story?id=4507808&page=1 it is claimed that

Short-haul flights are usually pressurized at 5,000 to 6,000 feet while long-haul flights are closer to 8,000 feet, according to Thibeault, [M.D., medical advisor, IATA].

But why would this be? My understanding is that the cabin pressure is chosen as a balance of:

  • what the aircraft can withstand without slow structural deformations, so that it is functional for many years
  • what is most comfortable for the passengers
  • most fuel efficient- pumping in air requires some fuel.

With regards to comfort, I should think that low pressures take their toll after a few hours (I think I read 3-9 hours, for people developing altitude sickness symptoms at about 8500ft equivalent cabin pressure).

The only guesses I have at why short-haul flights can operate at higher cabin pressure is:

  • the aircraft body won't have as much structural change with a short-term pressure difference

  • the plane can 'retain in' air pressure without actively pumping it for some time on the order of hours/ half-hours, so it is not so energetically costly.

$\endgroup$
  • $\begingroup$ For anyone else who read the title wrong: it says "higher cabin PRESSURE" (= lower cabin altitude) $\endgroup$ – J. Hougaard Sep 15 at 17:35
8
$\begingroup$

For the structural loading, the absolute cabin pressure is not as important as the pressure differential with respect to the outside pressure.

Short-haul flights typically operate at lower altitudes; either because they are operated by turboprop aircraft which have a lower service ceiling, or because there is simply not enough distance to climb to a high altitude and glide back to land. At lower altitudes, the outside air pressure is higher, and thus the cabin pressure can be higher without exceeding the maximum pressure differential the fuselage can handle.

Your other concerns are not really a factor. Only the pressurisation cycle count really matters to aluminium, not the total pressurised time duration. The fuel required for pressurising the aircraft is also not really a factor compared to the energy required to either heat or cool the air for passenger comfort.

$\endgroup$
  • 2
    $\begingroup$ The Boeing 777 is a long-haul aircraft that can cruise up to 43,000’, but not with a full load of passengers and fuel. At the beginning of a long-haul flight the typical cruise altitude is performance limited to about 29,000-31,000’. At these altitudes the cabin altitude will be only 5,000-6000’. $\endgroup$ – Mike Sowsun Sep 15 at 16:36
  • $\begingroup$ @MikeSowsun Exactly - it's the altitude that determines cabin pressure, not long- or short haul. $\endgroup$ – Sanchises Sep 15 at 16:57
  • $\begingroup$ Thank you for your reply. What do you think is the 'long haul/short haul' round-about cut-off (I realise that it will be dependent on many factors)? Would 2 hour flights, say, generally be flying at lower altitude? $\endgroup$ – Meep Sep 15 at 17:03
  • 1
    $\begingroup$ @Meep The long haul/short haul is from the older hub-spoke model, where jets would do long haul and turboprops short haul. This is still true in some places but in other places jets do flights under an hour at high altitude too, much shorter than some traditional short haul flights. $\endgroup$ – Sanchises Sep 15 at 18:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.