Header Bar Graphic
Shuttle Image and IconAerospace HeaderBoy Image
Spacer TabHomepage ButtonWhat is NASA Quest ButtonSpacerCalendar of Events ButtonWhat is an Event ButtonHow do I Participate ButtonSpacerBios and Journals ButtonSpacerPics, Flicks and Facts ButtonArchived Events ButtonQ and A ButtonNews ButtonSpacerEducators and Parents ButtonSpacer
Highlight Graphic
Sitemap ButtonSearch ButtonContact Button
 

Main WFO Banner

Hypothetical Airplane data

Using the data from the "Alpha" and "CM" columns of the chart, complete the graph on the next page. Follow the steps listed below.

First, plot the points for only "Run #1" from the "Alpha" and the "CM" columns. During this wind tunnel test, the elevator was set at 0 degrees angle of attack. The angle of attack is indicated by the data in last column which is the delta sub "e" (elevator deflection angle). Connect these points with a black line.

Second, plot the points for "Run #2" from the "Alpha" and the "CM" columns. During this wind tunnel test, the elevator was set at a positive pitch of +10 degrees. The angle of attack is indicated by the data in the column which is the delta sub "e" (elevator deflection angle). Connect these points with a blue line.

Third, plot the points for "Run #3" from the "Alpha" and the "CM" columns. During this wind tunnel test, the elevator was set at a negative pitch of -10 degrees. The angle of attack is indicated by the data in last column which is the delta sub "e" (elevator deflection angle). Connect these points with a red line.

Fourth, label point (0, 2) with the letter "A". This is the point at which the aircraft encounters turbulence. The nose pitches up. The pilot takes no action.

Fifth, label point (-0.002, 6) with the letter "B". The aircraft responds to the turbulence by pitching the nose back to its original position, so the airplane returns to point "A".

CM vs Alpha

CM vs Alpha

The time it takes the airplane to return to its original flight path after it encounters a wind gust is nearly instantaneous. No human even with computerized assistance could react as quickly.

Despite the differences in the angle of attack (as shown by the 3 similar slopes), a stable airplane upon encountering such minor turbulence will return to its original flight position. This will occur without the pilot having to take additional action. The test results you have just graphed demonstrate that this airplane is a stable airplane.

Wind tunnel tests never actually test for turbulence. A wind tunnel test is always performed statically. That means the aircraft is set in one position and air is blown by it. Data is recorded. The model is then set to a slightly different position and the test is repeated. A huge amount of data is gathered at each position. From these static wind tunnel tests the dynamic behavior (movements) of the model can be inferred from the data that's been gathered.


 
Spacer        

Footer Bar Graphic
SpacerSpace IconAerospace IconAstrobiology IconWomen of NASA IconSpacer
Footer Info