Every year there are cases of inadvertent flight into icing conditions. Either the pilot did not obtain a weather briefing, or he did not understand the potential for icing, or he disregarded that potential. In any case, rightly or wrongly he/she found himself with ice building up on the airplane.
The best thing to do, even with just a "smidgeon" of ice build-up, is to leave icing conditions immediately and attempt to get the ice melted off or removed. The question most pilots have in flight at such times is: Do I climb or descend? Or do I change course?
Not to be a smarty, but the answer is: Yes! If you've entered an area of precipitation that is isolated, then leave the area ASAP! If necessary, go back the way you came to get out of it.
If it's a wide area of precip and you don't know which direction to go, try changing altitudes. Hopefully you obtained a weather brief that included temps aloft. If it's warmer higher up, or it's significantly colder higher up, then that might be a good choice. Warmer air possibly will melt the ice or at least stop the build-up. Significantly colder air may stop it from sticking to the airframe. Wet snow can build up into airframe icing and if it's colder upstairs the snow may no longer be wet...but may be too frozen to stick. Same is true of freezing rain or sleet.
I personally always prefer to climb if that option exists for me, using the logic that if climbing doesn't stop the ice accretion then I still have the option to descend and try that. But if I descend and am still picking up ice, then any climb previously possible may be denied me due to the additonal ice upon the airframe and the resulting loss-of-climb performance.
In any case, an iced up pitot tube is not going to be helpful, and neither is an iced up propellor. And when you've gotten iced up, the windshield, if covered in ice, will make the subsequent landing pretty hairy! That little defrost that's available on later B-models is not very efficient and doesn't defrost a very large area either. Remember....it's not a windshield de-ice system. It's a de-FOG system.
Anyway... the topic that prompted me to bring up this subject is tailplane icing. I wondered how many pilots in this group have ever thought about it.
The tailplane (horizontal stabilizer/elevator group) works together with the wing and aircraft center of gravity (CG) to keep the airplane longitudinally stabile. The wing has upward lift (opposing gravity) and the CG of most aircraft including the 170's is forward of the center of lift (CL). The CL in most airplanes (and all 170's) is within the chord of the wing. In other words, the CL is located somewhere between the forward, leading edge of the wing and the aft, trailing edge of the wing.
The tailplane creates "downward lift"... a force in the downward position, which leverages the nose of the airplane upward (about the CL)so that the airplane flies level.
If you pull the cockpit elevator control (yoke/stick) aft, then the elevator itself is deflected upward, creating an overall effect of increasing the curve of the lower surface of the tailplane...and thereby increasing the "downward lift" of the tail. This pulls the nose of the airplane upwards as it rotates the fuselage about the CL.
Application of flaps causes the airplane to change pitch. This is because 1- the flap application moves the CL on the wing, thereby changing the CG of the airplane even farther from thef CL than previously, and ....2-the flaps influence the relative wind to deflect downward immediately in front of the tailplane. (The flap redirects or "blows" the relative wind downward in front of the tailplane.)
This is an immediate INCREASE in angle-of-attack for that tailplane! If that tailplane/horizontal-stabilizer has any ice on it at all, it is instantly subjected to a greater chance of tail plane STALL!
(This is similar to the situation when the B-model is slipped with full flaps... The tail plane is blanked out by the air flow past the flaps and it results in an abrupt pitch down. An iced up tail plane, however, will affect ALL models of Cessnas including the ragwings and the A-models.)
The wing is "thicker" than the tail. The leading edge of the wing therefore has a larger "bow-wave" and offers greater "warning" to the rush of oncoming relative wind...and any precipitation that relative wind contains, such as ice particles, snow, super-cooled water, etc. Therefore less ice will accumulate on the wing...than will accumulate on the tail. If you see 1/4" of ice on the leading edge of your wing.... there is SO MUCH MORE ICE on the TAIL...due to it's thinner shape. Therefore, when flying in icing conditions, the tail is always much closer to losing it's effectiveness than the wing. The tail loses it's ability to prevent a loss of control and rapid pitch-down much sooner than the wing loses it's ability to support the weight of the aircraft!
The result is usually a complete loss of control which catches the pilot by ocmplete surprise! He thought he had things under control because his wing was still holding him up there.... but he never realized he was about to become a lawn-dart because the tail was about to stall!
Adding a bit more speed to prevent this loss of effectiveness is a common technique. But... adding power to increase speed also results in higher demands on the nearly-stalled tail. If you have ice on your airplane, and you are approaching the airport under control....and you lower flaps in preparation for landing (thinking as usual they will increase needed lift) ... you may find yourself completely out of control, pitched down into the ground, and unable to recover! You must immediately retract those flaps to recover the airplane before the impact! The loss of altitude has been demonstrated by NASA to be 300 feet or more!
And guess what else? A wing-stall usually requires the addition of power, and the pushing forward on the yoke/lowering of the nose to recover from the stall. But... the tail-plane stall is EXACTLY THE OPPOSITE! A tailplane stall can be caused by the addition of power alone in some cases. A tailplane stall requires the REDUCTION of power and the BACKWARD movement of the yoke! This is the opposite of what most pilots have been taught. And it is insidiously deceptive.
The "feed-back" through the airplane's controls are almost imperceptibly different than when encountering a wing stall. In a normal wing-stall, the pilot feels a slight buffeting in the airframe and through the seat-of-his-pants. But in an approaching tailplane stall, he lacks that feel through the seat, and instead may feel a slight buffeting in the yoke only. He may feel a slight "lightness" or control-wheel force reversal, buffeting, "flutter" or...in some cases, he might even feel a forward-pull on the yoke as if someone is trying to pull the yoke right out of his hands. This is because as the tailplane stalls, a "void" is created in the lifting direction (remember? ... the downward lifting direction of the tail?) and the elevator will attempt to fill that void. The yoke may have an actual feel as if it is trying to go forward all by itself. The point is that if the elevator feels differently than ordinary and you have ice on the airplane.... WATCH OUT! Adding power or speed or flaps may cause a loss of control of the airplane!
Again: The tailplane will accumulate ice faster than the wing. Adding flaps will cause an increased tendency to stall the tail. And a stalled tail will drop the nose uncontrollably. It will be like someone CUT YOUR TAIL OFF! The recovery is to 1-RAISE FLAPS! 2- REDUCE POWER! 3-Be prepared to apply opposite elevator than normally experienced in a wing-stall.
Best thought: The Cessna 170 is not to be flown in icing conditions.