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“ ... the actual reason why there is an OAT limit is based on the ability of the oil cooler to keep the oil temperature from exceeding its limit.”
of saying, “The OAT that is 37°C above the standard temperature for that altitude.”
Therefore, at Sea Level, the King Air’s limiting OAT for operation is 52°C (15 + 37). This equates to about 125°F. Does it ever hit that sweltering temp? Sure, but it’s quite rare. Can you figure out what the limit is at 10,000 feet? Since the standard atmosphere experiences a drop of 2°C for every thousand feet, we would have decreased 20° from Sea Level to 10,000. That puts ISA at -5°C. Adding 37 more gives 32°C, or about 90°F ... mighty warm at 10K!
I heard from experimental flight test colleagues at Beech that the limiting factor for hot weather operation is the size and capability of the engine oil cooler. We all know that performance decreases as temperature increases. Although performance would definitely degrade, the actual reason why there is an OAT limit is based on the ability of the oil cooler to keep the oil temperature from exceeding its limit. As a side note, the fact that the Blackhawk XP67A engine modification to the 350 adds a fixed “cowl flap” at the oil cooler’s outlet yet still has an OAT limit 3° cooler than before – ISA + 34°C now – lends support to the assumption that oil cooling is the reason for the OAT limit. (If that poses an operational problem for XP67 airplanes based in hotter climates, a larger oil cooler is available that brings the OAT limit back up to the original value.)
When the model 200 first appeared, its POH stated that engine ice vanes could not be extended when the OAT exceeds 15°C. This applies to all operating conditions, including ground and flight. Again, we return to oil cooling considerations. Unlike the King Airs that preceded the 200 and those that came later with the “Pitot Cowl” design, the cowling used for the 200 series is unique. When the ice vanes are extended, the “bypass door” also opens to allow the deflected ice particles to harmlessly leave the cowling. Oil cooling suffers now
King Air Commuter Seats Now Available STC for the B200 and B300 models
Details
22 LB approximate weight savings on B200 executive seats.
30 LB approximate weight savings on B300 executive seats.
Leather upholstery.
Forward & aft facing seats available.
Transport Canada STC SA22-36 approval.
FAA STC SA00116IB approval.
Call or email us at
1-306-786-3360 reception@goodspiritair.com | www.goodspiritair.com
JULY 2024
KING AIR MAGAZINE • 21