captainglen

Just purchased a Davtron M655 for all the advantages I earlier pointed out. Wired a "T" connector harness which allows the Davtorn to power up from the transponder without actually modifying the transponder harness, You simply unplug the transponder from the encoder, plug the davtron into the encoder and plug the transponder into a connector in the davtron harness. I am still mulling over where to install the probe for best accuracy to avoid effects from sunlight and onboard heat sources. I really do not want to drill a hole in the bottom of a wing! which is the advised install position (any advice wound be appreciated) I discovered another advantage the instrument has in that calculating TAS allows you to skip a tedious step on the E-6B, you simply enter the density altitude and read TAS on the outer scale over IAS on the inner scale. You avoid the eye strain of trying to set the temprature over the pressure altitude while trying to fly the airplane at the same time. Digital E-6Bs are OK but with this method the old one is faster and easier! BTW spent $100 on the Davtron but had to spend $60 for a new probe.

Since the POH is in MPH a revised POH would be required for the airworthines certificate to remain valid. It is possible to revise the POH yourself but the approval process is cumbersome and sucess is unlikely. On the other hand it is unlikely to be detected except in a post crash investigation.

There are numerous advantages to a Davtron digital unit. The first of which is flexibility in where you mount the probe since it can be as much as 10' from the indicator. An obvious advantage is accuracy in calculating performance especially density altitude for takeoff performance. Another advantage is visibility they are illuminated and can be mounted in the instrument panel; just try reading an old style Aerotherm OAT gauge at night. Flexibility in that the Davtron instruments are multifunction, the simple ones also function as a Voltmeter/voltage alert while the more complex (M655-2) units display voltage,temprature, pressure altitude and calculate density altitude.