Stalling an aircraft

[bertengineer]

When practicing stalls in an aircraft, why does the nose fall forward if the aircraft is in coordinated flight, instead of just teater tottering back to the ground?

 

[TDTURBO]

If you continually hold back pressure it will continue to teeter-totter back and forth as long as its coordinated. It stalls, nose drops, airspeed builds, aircraft climbs(because your still holding back pressure) but with a high AOA or no power it will stall again and the cycle will repeat itself.......its kinda fun too.

 

[avbug]

Bert,

It doesn't always happen that way. Depending on the aircraft and the type of stall, it can happen just the opposite way. The nose may rise during the stall.

However, for most conventional aircraft, the nose falls through during the stall due to a decrease in downwash over the horizontal stabilzer (as opposed to the main lifting airfoil, the wing, simply giving up the ghost). This is more typical of a forward center of gravity. With an extreme aft center of gravity the opposite may occur during the stall.

Typically the buffeting you feel prior to the stall in light aircraft is a result of turbulent airflow over the horizontal stabilizer. As the downwash vector and intensity changes throughout the stall, the download on the horizontal stab decreases and the nose falls through on it's own. Rather than the wing falling down, it's the tail "falling" up. The result is that the nose drops, airspeed increases, the intensity (mass and velocity) of downwash over the horizontal stab increases, and the cycle repeats if control inputs are held.

Often a stall and the subsequent "dropping" of the nose is explained as a loss of lift over the wing due to airflow separation. While this is happening and is true in regard to the pattern of the airflow, it is an incomplete explaination as to what actually causes the nose to drop. This is caused by a change in airflow over the vertical stab.

 

[mattjenna]

This is caused by a change in airflow over the vertical stab.

Avbug I assume that was a misprint and you meant horizontal?

Matt

PS thanks for a concise explanation with clarity.

 

[avbug]

Matt,

Thanks. Yes, I did mean horizontal. This is my problem when attempting to translate my usual mumbles and handsignals into something coherent on the computer. Ordinarily I'd make the same mistake while speaking, but would clarify it with a series of mime-like handsignals that resemble a cross between sign language, spastic behavior, and a street corner display for nickles and quarters. ( To my great relief, no one has tried to throw a defibrilator on me yet, while I'm trying to explain something in person).

Also, the pitching moment is due to an air temperature change in the fetzer valve...

 

[A Squared]

>>>>>....To my great relief, no one has tried to throw a defibrilator on me yet......

yes, but do they throw nickles and quarters at you???

 

[avbug]

Yes, if I put my hat on the ground first. Sometimes the men in the white coats come. Usually when people do throw things, they throw them really hard. I turn it to my selfish benifit, however. When I go through the metal detector, I make a point of counting out the coins one by one. Then, just before getting to number three hundred and sixty four, I lose count and start over.

It's possible to get through based on nothing more than the fact that no one wants to deal with you any more. Sometimes, that's a good thing.