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Touring Motor Gliders Association (TMGA)
  • Easing the Demand on the Engine on a Hot Day

    Ethan Graham

    Abstract: We have a 2400 CC engine that tends to reach, and exceed, red mark limit of oil temperature (120C, 249F). Has anyone addressed the problem of oil overheat in the Taifun?

    Subject: July 6th Soaring Flight in Southern California
    From: "gurrini" <gurrini@
    Date: 7/6/07 7:48 PM
    To: Taifun17E@yahoogroups.com

    While the Los Angeles basin was choked in smog July 5th, created by an intense inversion, cumulus appeared over the northern section of the San Gabriel Mountains. The inversion was obvious from the Pasadena 1,000' elevation temperature of 87°, with 6,000' nearby Mount Wilson at 102°, and the Barstow 3,000' desert at 118°. See the attached photo taken from Mount Wilson. The lapse rate was quite steep on the 5th with more of the same existing on the 6th, while temperatures were forecast to be about 6° cooler. This can be seen in the attached San Diego skew chart.

    After a 12:15pm take off in 95° windless humid conditions, the Taifun climb was very slow, using less RPM and higher airspeed to keep engine temperatures below redline. Climb outside air temperature was 95° at 7,000'. Only one weak thermal and a lot of sink existed everywhere over the mountains in moderate chop. Thirty nine minutes later, 9,000' was reached over Mount Lewis, a long time reliable peak. Then an abrupt violent surge up to 15,000' with lift as high at times at 7 knots took only 9 minutes. A characteristic of moist south flow with an intense Southern California inversion coupled with a very steep lapse rate aloft.

    During the course of a nearly four hour flight, lift went strongly to cloudbase at 17,980', where the outside temperature was 25°f, with obviously strong lift continuing higher in cloud. Much of the flight time was was above 15,000'. A lenticular cloud extended from the Cajon Pass westward to Mount Lewis, under which the lift was about 2 knots, enough for straight cruise almost holding a steady 16,000'. A final glide from Mount Baldy starting at 15,500' took 43 minutes to descend in very still stable air to 4,000' near Whiteman Airport, averaging
    267 FPM.

    This is a typical hot muggy California desert day where towed sailplanes never can get much lift in the inversion, but a Taifun can "motor cheat" and make a great flight. I've been soaring in Southern California for (46) years, and have seen plenty of these days. I was ready when this one arrived

    Subject: RE: [Taifun17E] July 6th Soaring Flight in Southern California
    From: Haim Zaklad <zaklad@>
    Date: 7/6/07 11:50 PM
    To: Taifun17E@yahoogroups.com

    Indeed a great flight that reiterates a point- Do not be discouraged by a thick inversion layer (the adversary of the glider pilot).

    In Israel, on certain hot days, we may have good laps rate above an inversion but if the trigger point is not reached, no glider pilot is giving it a chance (but we have a Taifun and mountains at a distance worth flying to….)

    And now to the point:

    We have a 2400 CC engine that tends to reach, and exceed, red mark limit of oil temperature (120C, 249F). RECALL THAT BEST OPERATING CONDITIONS ARE 80C, 175F. We worked with the very cooperative Peter Solomon of Limbach to solve this problem. Peter advised us that this is not an unusual complaint by Taifun owners flying on hot days. He also indicated that 10C overheating (i.e-130C!!!) is tolerable. Peter sent us a more powerful replacement oil pump and a double oil radiator. These measures helped a lot but still, we must ease the demand on the engine on a hot day to avoid the red line.

    Has anyone addressed the problem of oil overheat in the Taifun?

    Haim Zaklad


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