I was enjoying a cross country flight with my C152II in Sweden. I was climbing to 4000 ft at a rate of 500FPM when suddenly my airspeed indicator went from 70-80KT to 0. I was still moving forward and continued my climb and everything else looked normal, so it was not a computer freeze. The airspeed indicator stayed at 0 for about 15 minutest and then came back and worked normal for the rest of my flight. Now, my question: did I encounter some sort of bug, or is this a feature? I was thinking it might had been due to cold weather or something. I am not a real pilot, and I am new to the C152, so I don't have that much knowledge of what to expect... Any thoughts?

You are probably correct with it being a standard feature,

You probably had pitot heating off, so the tube froze.

 

http://en.wikipedia.org/wiki/Pitot-static_system

Sara has it right.

 

Any time you're flying in conditions that might cause icing, your first indication of a problem is the airspeed indicator falling to zero. The airspeed indicator is driven by the pitot tube, and you correct it by turning on pitot heat to remove the ice. You should get your airspeed indicator working normally in about 30 seconds maximum. One way I use to determine if I'm still in icing conditions is to turn off pitot heat and watch the airspeed indicator. If it falls to zero, I'm still in ice.

 

Pitot tube freezing isn't the only problem with icing. You're probably picking up carb ice as well, and you need to turn on carb heat to get rid of it. You know you've got carb icing because your engine will lose power, and can eventually stop. Turning on carb heat usually restores engine power immediately. If you suspect carb icing, turn on carb heat. If the engine power (and RPM) picks up, you know you've got carb icing. The carb is less likely to ice up under high power, so it's normal to add carb heat any time you are descending. Note that carb heat will cause a slight power reduction. I've been in icing conditions even on the ground, where I had to use carb heat during the taxi, just remember to turn it off when you go full power for takeoff.

 

Another problem with icing is that you're picking up ice on the airframe. The maximum ice was probably about 10 minutes after your airspeed indicator went to zero, depending on how severe the icing was. Airframe icing acts very similar to increasing the gross weight in FSX, and by the 10 minute point you should have noticed some differences from the normal flying characteristics of the aircraft, including flying at a nose high attitude in level flight compared to non-icing conditions. Unless the aircraft is equipped with deicing boots or another mechanism to remove the ice, there is no way to get rid of it short of flying out of the area where icing is present. Some aircraft have additional prop deicing mechanisms, but not the one you were flying.

 

You can fly out of icing by descending (preferred), climbing, or flying beyond the icing conditions. Since you probably don't know how high or low or how far the icing conditions extend, this is a very dangerous condition. I once got into severe icing, turned on pitot heat, carb heat and prop deice, but had no way of removing the airframe ice. By the time I realized I was in trouble, it was almost too late to divert to the nearest airport, where I sat on the ground in time compression for a considerable period waiting for the ice to dissipate. Landing what acted like a severely overloaded aircraft was... interesting.

 

Best to avoid icing conditions whenever possible unless totally equipped for it.

 

Hook

Wow, thanks for the answers guys. Seems like Carenado has done a good job. That is really a COOL feature! I think I had the pitot heat on, but probably I didn't...