Icing and PIREPs
Perhaps the reason there is a significant shortage of PIREPs is because not many pilots fly in the weather likely to make a PIREP important. PIREPs are especially good when they are about icing and turbulence but they are often just a snapshot and lose validity unless the pilot can fill in the whole picture. According to FAR 91.183 an encounter with unforecast icing requires a PIREP. The giving of a PIREP should be an independent communication and not given as a part of routine route information. The rate of ice accumulation is more important than the kind of ice. The AIM has an ice accumulation rate table which for accuracy must be judged by someone who flies only in ice. War story example follows:
Prior to a late fall afternoon Reno departure for the Bay Area with a stop at Truckee, I visited the Reno FSS and studied the satellite pictures. The route had clouds above 12,000' with icing in clouds. The flight to Truckee was uneventful but it was apparent that the cloud level was less than 12,000'. Prior to our Truckee departure we made radio contact with FSS which confirmed lowering conditions with icing in clouds. On departure we monitored the FSS and were advised that just a few minutes before a Cessna flying out of Reno on a route slightly south of our planned route had reported moderate icing and hail.
We advised the FSS that we would take a look before canceling the flight. We proceeded below the clouds to fly via Interstate 80 to Sacramento. We maintained contact the Reno FSS until we started our descent into the Central Valley. Without my previous visit to the FSS in Reno I would not have had the bigger picture which showed the worst of the weather to be southeast of our planned route. Even with the lowering clouds there was ample margins of safety related to freezing levels and no visible precipitation along the route. A PIREP along our route would have given us a couple more days in Reno.
Forecast icing. according to the NTSB, is the same as known icing. The fact that the entire flight was VFR without any precipitation meant that by picking our route carefully we avoided both weather and FAA problems Last year I did inform ATC that we had snow in the cockpit. I don't know what conditions caused the cockpit snowstorm but precip filled the cockpit for about ten minutes. On another flight the same year asked ATC for higher so my student could get some actual. At 13,000 we got into a cloud that caused a rapid accumulation of rime ice. We immediately asked for lower and proceeded at 11,000 as the ice gradually disappeared. In every one of these icing encounters I always maintained continual radio contact and radar if altitude permitted. I have kept backdoor openings for every icing encounter. ATC is required to get PIREPs when a ceiling is below 5000' or 5-mile visibility. An ATC request for flight conditions is a request for a well-constructed PIREP with special reference for thunderstorms, icing or turbulence.
Incidentally, there is no record of the FAA violating a pilot for having presented icing PIREP. Declaring an emergency because of icing is a viable option regardless of the consequences since it assures you of any help you may need short of deicing ability.
The system relies on good PIREPs. PIREPs are used to expedite traffic. A SIGMET or AIRMET can be issued based upon a well reported PIREP. Many thousands of commercial aircraft now carry the Aeronautical Communications Addressing System (ACARS) that report winds and temperature. The Future GPS downlinks will be capable of continuous meteorological data downlink streams.
Without 'known icing' ability you should stay out of visible moisture when the outside air temperature (OAT) is below freezing. Part 91 flights are prohibited from flying into known icing. FAR interpretations consider forecast and known as identical.
Flight in Icing
All exterior sensors, pitot, static, and stall warning will be degraded as to sensing ability and accuracy. Antennae efficiency can be changed. I have had radio transmitter relays freeze in the cockpit so that they would not operate for transmission. (We used a handheld) Propeller unbalance is common. Fly at faster speeds than normal in climb, descent and especially landing. Most icing happens in visible moisture with temperature between zero and -14 C. Less than 10% of ice accidents occurred when ice was worse than forecast. No aircraft is certified to fly in moderate freezing rain. Any flight into forecast icing is considered by the FAA as a violation of FARs 91.9 and 91.13. by exceeding operating limitations and being careless and reckless.
As ice accumulates and lift decreases, the pilot must increase the angle of attack to retain lift for level flight. In this condition ice begins to accumulate beneath the wind and tail surfaces. You can't see ice below the wing in many aircraft. Any de-ice capability should be used only to escape the icing, not to continue the flight. You cannot afford to be casual while operating in ice. You need to be current in your skills related to unusual attitude recovery.
Carburetor ice is far more likely to occur and cause an accident than is airframe icing. 51% of icing accidents are caused by carburetor ice or induction system ice. The cause of this ice is the failure of the pilot to ANTICIPATE the possibility of ice by applying full carburetor heat and alternate air. The fixed pitch plane will develop a rough engine while the constant speed plane is going to show a drop in rpm. Under icing the C. H. will increase the roughness of the engine. Leave it on. Use alternate air if available.
Icing
0. The one-hundred-eighty turn is on record as having saved more lives than governmental inertia have killed.
1. Visible rain at below freezing temperatures
2. Splashing or splattering rain drops at below freezing temperatures
3. As for immediate priority ATC handling
4. Avoid abrupt or excessive maneuvers.
5. No autopilot
6. Reduce angle of attack if aircraft tends to roll
7. Do not extend flaps
8. Do not retract flaps if extended.
9. Report conditions to ATC
10. Structural icing is least likely to occur in high clouds since they are formed mostly of ice crystals.
11. An encounter with ice pellets is indicative of freezing rain above.
12. You know that if you fly into rain that freezes on impact that the temperature is warmer at a higher altitude.
13. If you encounter wet snow, you known that the temperature is warmer than freezing.
14. A surface inversion is most frequently produced by terrestrial radiation on a clear calm night.
15. The surface temperature being below the dew point with the air and dew point below freezing causes Frost. Water vapor then sublimates directly as white and opaque ice crystals or frost.
16. Whenever icing is a hazard it will be forecast in sigmets and airmets.
17. Standing lenticular clouds are indicative of severe turbulence.
Tail Stall
This stall can occur when ice accumulates on the bottom of the horizontal tail surfaces to such an extent that the flow
of air ceases to give the required download. The tail stall occurs on the bottom side of the horizontal tail surface.
This lack of airflow can be even further reduced with the application of flaps and an increase in airspeed. Flaps will increase the downwash angle of the over tail air stream and increase the negative angle of attack. This can result in an abrupt nose down attitude and descent. The recovery is completely different from a normal stall recovery. Flaps are removed. Power is reduced and the yoke is pulled back. Pipers are subject to this more than Cessnas.
The do not use flaps if icing exists or is suspected. You will not be able to see ice on the bottom of the horizontal tail
but any ice accumulation will occur there first. Fly the approach at a speed that will account for ice created drag but
not extra fast that will increase the downwash on the tail surface. More downwash increases the tail stall possibility.
So long as airflow stays attached to the bottom of the tail, it is flying. You will have control and down pressure from
the tail.
The full stall does not occur until both the low-pressure (top) of the wing and the (bottom) of the tail surfaces lose
all their lift. (I urge you to think through the "download" effect of the tail surfaces since it is often part of the Practical
Test oral.) This doesn't happen. With all low pressure surfaces having some effect the aircraft does not go straight
down. The tail is being held down by low pressure below the horizontal tail surfaces. With ice on this surface it will
have reduced effectiveness and power. If flaps move the center of lift for the wings backward an abrupt nose down
pitch is most likely to occur.
The tailplane will collect ice more readily than the wing. The collected ice will more adversely affect the tail-plane's downward loading than would the same amount of ice on the wing. Ice may be on the tail before appearing on the
wing. Boot deicing on the tailplane is less effective than on the wing. An icing tailplane stall may be unrecoverable.
The icing you get may be quite different from the icing used for certification. The tailplane may be colder than the
outside air temperature (OAT)
Advice: Don't use flaps if you suspect ice. Don't mess with ice. If the freezing level is on the ground, you won't be
able to descend to warmer air.
Survival Kit
1. Textbook ..........................16. Compresses
2. Waterproof matches/tinder 17. Tapes
3. Water-flexible package .....18. Aspirin
4. Space blankets/tarp ..........19. razors
5. Multi-Knife .......................20. Signal mirror
6. Fire starter ........................21. 5-day rations
7. Large trash bags ...............22. Bouillon cubes
8. Flashlight ..........................23. whistle
9. First aid kit .......................24. Survival saw
10. Take compass from plane 25. Survival candle
11. Insect repellent ...............26. Chemical lightsticks
12. Sun screen/balm .............27. Gloves
13. Hacksaw blades .............28. Hard candy
14. Vice grip/ pump pliers .....29. Toilet paper
15. Sealable container ..........30. Razor blades
Survival Basics
1. Get out NOW, take what you can.
2. Treat injuries, stop bleeding, keep warm, immobilize
3. STOP
S is for STOP
T is for THINK
0 is for OBSERVE
Knowing where you are is half the solution
Mark any trail used.
P is for PLAN
Select a leader, conserve energy, improvise.
Fears in Survival Situations
The unknown, darkness, discomfort, being alone, animals, death, punishment, and personal guilt.
Enemies of Survival
Yourself, injuries, temperature, disease.
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