casm wrote:
Any info on best economy figures for cruise speed & fuel consumption for the T303 at say 65% power (LOP & ROP)?
I use the rule of thumb formula HP * % power *0.078 which usually works for normally aspirated engines, on turbocharged engines I would add 1-2 USGPH to get an estimate.
It was advertised as 200 knots at FL200, but at FL100 presumably the laws of physics apply and 160KTAS might be realistic, using 27USGPH?
Does anyone have real world mass data for a 340? Especially the empty mass, MTOW, maybe MZFM?
A colleague who flew Cessna twins back in the day when they were much younger had an interesting reminiscence. An owner decided to trade up from a Pressurised 337 to a 340, but after six months regretted it. He claimed the P337 was faster, cruised higher more comfortably and, what most would agree on, was much more versatile in handling short or unimproved strips. The mission had remained the same, 500nm sectors IFR around Europe. This owner/pilot described the P337 as a real pilot’s airplane. The 340 also could end up with a relatively skinny payload when tanks were full.
Apparently a few operators tried to put the 340 on a UK AOC, but never managed to satisfy the performance requirements – this is likely to be the early 285 HP engine version. Alternatively it may be due to the TODA at their bases, typically around 900-1100 metres.
Any info on best economy figures for cruise speed & fuel consumption for the T303 at say 65% power (LOP & ROP)?
I fly my PA46 piston at MTOW almost all the time I do a serious trip and it climbs less well than Jason’s did, takes me about 38min to get to FL250. I prefer to stay around FL180-FL200 usually, I feel like I’m being kind on my turbos by doing that, but if weather or ATC favours a higher (or lower) route I’ll have no hesitation.
ortac wrote:
What do the PA46 (piston) pilots on here consider to be a practical ceiling, in terms of reasonable time to top of climb? I can’t see that a 340 would do worse than this, unless very heavy.
For the piston I flew mine at 240/250 all the time but many people tend to only fly them in the high teens low 20s. Time to climb was around 30 mins for 250 on a normal day.
https://www.twincessna.org/twin-cessna320.htm
The Skyknight was a top dog in its day with 220 KTAS – I still remember the marketing brochure with owner fondling a Purdie, black lab looking up loyally, wife/girlfriend in a cocktail dress in the background…marketing straight out of the Hefner world.
Great looking alpha twin and one keeps being advertised in Pilot.
Indeed. 10,000ft is probably marginal for smokers and other unhealthy people out there, of which the numbers are increasing unfortunately. But I wouldn’t hesitate to climb to 10k cabin altitude if I needed to as do that unpressurised already.
The 340 maintains a 8,000ft cabin to 20,100ft and 4.2psi thereafter so 23,500ft ceiling for 10,000ft cabin.
I think the 8000ft cabin altitude also comes from some other stuff, to do with medical limits on the carriage of passengers in “less than perfect health”.
For example the portable oxygen units in widespread use (visit your local hospital outpatient waiting room, anytime) – this is one of many vendors – tend to be rated to 8000ft only.
We did this in several threads in the distant past – example. Most of those units are accordingly useless for our aviation use.
I have come across the 8k feet cabin altitude before as the maximum allowable in airliners.
That’s a part 25 certification requirement (no. 841 if you want google to find it more quickly). This kind of stuff is not part of the normal ATPL syllabus. A C340 is certified under part 23 so it does not apply.
