I was up in a C172 the other day working on slow flight and flying on the very back of the power curve with my instructor and I could get the ASI to stand on 0 knts without stalling the aircraft. This was not because we were doing 0 knts, but because of the high nose pitch and of the angle of the air hitting the pitot tube. However, when I try this in the C172 in FSX I can get to 40 knts but if the ASI drops under 40 knts the aircraft stalls. My question is, can you fly on the backside of the power curve in FSX, or is the aircraft.cfg written to stall under 40 knts indicated? Or was I just pitching up way to high because of the lack of 'pressure' you get on the controls in a real aircraft?
(I have the airspeed set to display indicated speed, instead of true.)

Also can you flying in slow flight (in the sim) with the stall horn sounding like you can a real aircraft (because in the real 172 the horn starts sounding around 5-10 knts above stall speed)?

   Thanks, I thought the flight dynamics where a little funny outside of the the 'normal' flight range. As for getting 0 knts indicated, I'm not sure how that happened. All I did was, full flaps, slow to 55 knts, full power to maintain level flight, slowly pitch up higher, and the airspeed indicator unwinds like crazy, the stall horn sounds, and balance the pitch enough so the airframe buffets, but doesn't fully stall.

I'll ask my instructor about it next lesson. Maybe it was magic...

Brett_Henderson wrote on Jul 6^th, 2009 at 11:45pm:


I know all about that, a C150 with full fuel, hot day, strong headwind and a overweight flight instructor.

"...985GH turning base to final for runway 6...number two behind the kite..."  


Sorry about that I meant groundspeed not airspeed. I guess this is what happens when you post late at night.

I asked my instructor if it was possible to get 0 knts on ASI in slow flight, he said you can. What will happen in very slow flight is the area of low pressure under the wing begins to move forward and above the wing, and the low pressure flowing forward and above the wing will stuck air out of the pitot tube instead of the ram air going in. He said it is the same principal the stall warning horn works on.

Ravang wrote on Jul 8^th, 2009 at 4:24pm:


I like these discussions, but I'm gonna circumvent the hair-splitting. I've taken a C172 in and out of slow flight enough to know that by the time the condition you've described happens (I've yet to see it)... you've long-since stalled.  .. unless it happens for a brief period during an abruptly entered, stall..(continued in my next post).

**also.. (per your original post).. older ASIs simply stop responding accurately below 40 knots.. so your experince is possible ... it's a shortcoming in the equipment (why I suggested an inspection), not because of the AoA.

Brett_Henderson wrote on Jul 8^th, 2009 at 9:32pm:

I think you hit it on the head with the older ASI stuff. The aircraft is a 1981 model Skyhawk so it probably still has the original ASI. But common sense will tell you, 0 knts in controllable flight is not possible in a Skyhawk.

I may have fudged up my instructors definition of how it happens, because his nerdy definition involved a lot of math problems, aerospace engineering terms, graphs, charts, and what looked like nuclear launch codes to me....

So he was talking about airflow dynamics over an airfoil and pressure dynamics, or a tuna sandwich...

I'm a very visual person, I can show you what I'm talking about, but I can't describe it worth a dang. If you show me I'll get it, if you write it, well, I'll think your talking about sandwiches. Sorry about all the hair you've pulled out during this thread...

Cover that airspeed and fly the same maneuvers.  Feel that Skyhawk start to give up and when the yoke's all the way back and the throttle's firewalled, be thankful for your altitude.  It may not spin but it'll be descending like a brick.  For a more vivid experience, put two people in the back.

A Cherokee 140, that no good flat spinning piece of s##t.  You couldn't go out and do anything slightly funny unless the CG was way forward and there was only X (I forget) gallons in each tank.  Part of my CFI ride was spin demonstration in a PA28/140 and the FAA guy said he'd observe from the ground.  Smart - it never really spun but he was happy.