Friday, May 31, 2013

Variations and Training

Variations and Training

Since there are no Flight Data Recorders required by Regulations to be installed in Light Twin Engine Airplanes, Air Operators of these types of airplanes are not require to monitor and record altitude and airspeed during flight. However, the majority of light airplanes today are GPS equipped where flight parameters are available. 

Common Cause variations is Normal Operations and Special Cause variations is Emergency Operations. 

There are two segments to the chart, where the first is normal flight conditions and the second where the airplane enters into a thunderstorm. 
 Departure airport elevation is 3500ft, mountainous area with peaks to 10000ft and destination airport elevation is 3500ft. 
The climb up to cruising altitude of 12000ft is normal. At 12000 the pilot levels off, maintaining airspeed of 165kts. 

The airplane enters into a slow climb with a slight reduction in airspeed. At 12300ft the airplane suddenly drops down to 12000ft. 
Shortly thereafter the airplane descends with a slight increase in airspeed.  At 11700ft the airplane climbs back to 12000ft. 

The flight enters into a thunderstorm and there is a drop in airspeed to zero and the airplane climbs to 15000ft. Just as sudden as it climbed, the airplane drops down to 11000ft. The airspeed suddenly comes back, increases to 190kts and the airplane again climbs to 15000ft, where the airspeed decreases to 120kts, the airplane drops to 11000ft and then climbs back up to 12000ft. 
Next thing is another increase in airspeed, climb to 15000ft, with a sudden drop in speed to 55kts and drop in altitude from 15000ft to 11000ft. Shortly thereafter operations are back to normal with cruising altitude of 12000ft and 165kts.
The first segment of normal flight is Common Cause variations, where the pilot is not attentive and allows the airplane to climb and descend beyond acceptable altitude limits. Training for Common Cause variations is training for Normal Operations, where an Air Operator may apply training to enhance pilot performance.

The second segment of thunderstorm is Special Cause variations, where airplane is performing by the forces of the thunderstorm. Shortly after entering, the Pitot Tube ices over and airspeed goes to zero, followed by a force lifting the airplane to 15000ft and then drops it down to 11000ft. Airspeed comes back, airplane is hit with an updraft with an increases in airspeed to 190kts. This is followed by a downdraft and the pilot is attempting maintain altitude by pulling back on control column reducing the speed to 120kts. 

A final blow to the flight is when a severe gust causes one wing to stall at 55kts and the airplane enters into a spin.  

SMS is to use tools available and to be moving forward. 
SMS is not to get stuck in the past with old Systems
Altitude and speed variations beyond acceptable limits due to thunderstorm are Special Cause variations and require different training than Common Cause. Variable cause training is training for Emergency Operations.    

By applying GPS parameters Air Operators have an SMS tool available to collect and analyze data, apply this knowledge in developing Training Programs, to increase Safety Margins and to elevate level of Customer Service. 



  1. Data is always important post incident. The problem is the data needs to be analyzed and then used to determine what needs to be done with the system to prevent the incident in the future. We can't so nothing about the weather...yet. So we need to analyze the decision to fly into a storm area. This is where risk analysis comes in. Should the plane have been in that area? Data is essential, but if not is worthless.

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