Estimated vs Flight Test
Lonewolf 50,
Thank you for your response. You are right, it would be difficult establish exactly what estimated means. The H-53E HV charts are also labeled estimated even though the single engine failure data points were verified during contractor flight tests at Patuxent River in the early 1980s.
Also, I believe that some of the data for the E model was brought forward from the D where actual full touchdown autrotations were performed during development. Discussions with one of the pilots that actually did the full touchdown autos lead me to believe that forward ground speed at touchdown was the major issue. The length of the airframe dictated the flare pitch attitude. The higher the pitch attitude resulted in a higher flare altitude above ground. The best combination of pitch attitude/altitude resulted in touchdown speeds between 40 and 60 kts. Anything slower resulted in a significant increase in touchdown rate of sink.