Pre-Flight: ADC altitude variables PALT_A, PALT_A2, and PALT reporting as ~-27 meters. All tracking each other closely. Attempted reset of of AC server and AENT device #2 without result. All other values for ADC look within normal range. Novatel Altitude looks good. Follow up from Catherine indicating negative altitudes are fairly common at sea level.
2DS array voltages all above 1.9 V. Very little false particle trigger on the ground. 2DS RH at 15 percent
Flight:
1811 - ushas reset 1823 - 2ds particles detected 1837 - lost down facing camera due to software issue. Chris W resolved at 1838 1909 - power cycled down camera POE injector for Catherine 2320 - restarted VCSEL 0005 - Near total occlusion of the 2DS horizontal channel. Applied mask effectively disablin any particle detection.
- Sporadic connection to down camera throughout flight. likely a connector issue under the floor. no action taken in flight. - Research power was lost on the transition from engine to apu after landing
Since it is pressure altitude, it is computed based on atmospheric pressure. Sea level is defined as 1013.25 mbar. A high pressure can exceed that, driving the altitude negative. If you have an altimeter watch, that is pressure altitude, and why the altitude at your house floats plus/minus a few hundred feet.
2 Comments
Richard Freeman
RF05
Tech: Richard Freeman
Date: 20 April 2022
Takeoff: 1759Z
Landing: 0158Z
Pre-Flight:
ADC altitude variables PALT_A, PALT_A2, and PALT reporting as ~-27 meters. All tracking each other closely. Attempted reset of of AC server and AENT device #2 without result. All other values for ADC look within normal range. Novatel Altitude looks good. Follow up from Catherine indicating negative altitudes are fairly common at sea level.
2DS array voltages all above 1.9 V. Very little false particle trigger on the ground.
2DS RH at 15 percent
Flight:
1811 - ushas reset
1823 - 2ds particles detected
1837 - lost down facing camera due to software issue. Chris W resolved at 1838
1909 - power cycled down camera POE injector for Catherine
2320 - restarted VCSEL
0005 - Near total occlusion of the 2DS horizontal channel. Applied mask effectively disablin any particle detection.
- Sporadic connection to down camera throughout flight. likely a connector issue under the floor. no action taken in flight.
- Research power was lost on the transition from engine to apu after landing
Christopher Webster
Since it is pressure altitude, it is computed based on atmospheric pressure. Sea level is defined as 1013.25 mbar. A high pressure can exceed that, driving the altitude negative. If you have an altimeter watch, that is pressure altitude, and why the altitude at your house floats plus/minus a few hundred feet.
I have also seen negative GPS altitude in the past, but not recently. GPS altitude is based on how good the geoid definition is. The first 25% of this page should be useful: https://enterprise-insights.dji.com/blog/geoid-vs-ellipsoid