Operating Tips for an Icing Encounter in the Cessna Caravan

Operating Tips for an Icing Encounter in the Cessna Caravan 

In the Northern Hemisphere Winter is right around the corner, and with it comes increased chances that the Caravan that you fly will have an icing encounter. Are you familiar with the various steps that you can take to help manage the impact of an icing encounter? Whether you own, fly or manage a Cessna Caravan, we here at Caravan Nation recommend that you, not only read this article, but print and save the below listed operating tips for future reference.

The operating tips listed below are part of the FedEx Caravan Icing Program. A program that you should acknowledge and possibly incorporate it into your own program. 

In the Caravan, like every other airplane, you can help manage the impact of an icing encounter by remembering two general rules: 

A) Keep the airspeed/power up and, 

B) Keep the deck angle/AOA down. 

Additionally we recommend that you consider the following:

1. Make sure that you receive a thorough weather briefing. Know the right questions to ask, and don't hesitate to ask them.

2. Compare frontal movement with the proposed flight path, remember to look well up-wind of your course line to see what kind of weather is approaching your flight path.

3. Pre-flight ALL of the aircraft anti/de-ice systems for proper operation and cycle sequences.

4. Periodically wax areas of the aircraft that are exposed to ice accumulation: e.g.

• Nose wheel fairings & accessories (not the shock)
• Engine cowling
• Cargo pod
• Wing-strut/wing-joint area including tie-down hook
• Main landing gear dressing including brake-pad housing, but not the brake-disk
• Gurney-strip of the trailing edge of the flaps
• Left & right outer elevator horn

5. Exercise self-discipline and try to envision ALL possible "What if (s)" that might be encountered during the initial take-off and climb in icing conditions.

6. Use of flaps for take-off should be carefully evaluated when icing is anticipated during departure.

7. Remember... snow, slush, or water standing on the runway will greatly increase the required take-off distance, as well as landing roll. Be particularly careful when a take-off is being conducted. Slow acceleration to liftoff speed followed by an ABORT will require considerably more runway. Therefore, where a choice can be made, pick the longest runway for both take-off and landing.

8. After take-off, increase speed to 110-115 kts as quickly as possible. This will help keep ice formation on the protected areas of the aircraft. Continue to climb with a minimum deck-angle.

9. At airports where SIDs are used, pick a direction of departure which has the lowest climb-gradient. Once you are at a safe altitude you can then proceed to your destination.

10. Constantly monitor & assess the icing situation of your aircraft. Be particularly alert to OAT changes during the climb. Observing the OAT during your climb to altitude can provide clues which could save your life.

11. Consider not using the auto-pilot when operating in ice. This is not to imply that the auto-pilot is not approved for ice operation, but that a pilot can not possibly know how the aircraft is FEELING if the auto-pilot is engaged.

12. When encountering icing and the airspeed begins to drop below 130 KIAS, MAXIMUM CONTINUOUS POWER e.g. 1865# torque/805 C ITT (675 HP) as applicable, should be used.

13. De-ice boots are more effective at higher airspeeds. At lower speeds effectiveness may be improved by SMOOTHLY changing the pitch attitude as the boots are being MANUALLY inflated which will allow the changing relative wind to assist in removing the ice from the wing leading edge.

14. A vibration may occur as ice starts to build on the propeller hub and the back side of the blade near the hub. Under extreme conditions the vibration may continue to increase the the point where the instrument panel begins to shake. In conditions of MODERATE and above accumulation rates, the automatic propeller anti-ice system may not be sufficient to keep the propeller clear of ice. Under these conditions, consider using the MANUAL propeller anti-ice feature and briskly cycling the prop between the maximum and minimum RPM (minimum 200 RPM change) to assist in removing the ice.

15. Don't keep flying into deteriorating conditions. Have a plan, e.g. climb, descend or turn to get to less severe conditions if it become necessary. KEEP YOUR SITUATIONAL AWARENESS AHEAD OF THE AIRPLANE. DON'T ALLOW YOURSELF TO RUN OUT OF OPTIONS!

16. Communicate your situation with ATC. Keep them advised of your icing problems. Asking for help is not a sign of weakness. Failing to use all of the resources at your disposal is sellling yourself short. DON'T LET A MACHO ATTITUDE OVERLOAD YOUR BOAT!

17. Monitor the terminal approach frequency while you are still in the enroute portion. This will allow you to listen-in on any problems other pilots may be encountering while in their attempt to land. During the approach keep your air-speed at least 15-20 knots higher than normal. Stall speed increases with ice accumulation.

18. Do not cycle the boots during landing since boot inflation may increase stall speeds by as much as 10 knots.

19. Fly the aircraft down-to-the-ground, do not attempt a normal flare-out to a stalled landing.

If you have any questions about this article, use the contact form on  CaravanNation.com 

Always remember to... "Never stop learning. Review often and never get complacent so that you can continue to fly safely!"

AirNationGroup.com

 

Too Cold for Ice by Bob Tilden

A Night Express Caravan being de-iced with heated propylene glycol.

Too Cold for Ice 

by Bob Tilden

"I would enjoy this kind of weather from now until April" was a common expression during the last two winters. We had many mild spells, and few snow storms. Expressing a sentiment towards the sort of winter that meets your own personal preferences is probably a selfish thought, but since we have no control over the weather, its probably forgivable too. Us normal folks should respect the fact that some people spend their summers hoping for a cold and snowy winter.

The last few weeks seem to show a trend for a cold winter in the northeast, and it suits me just fine. In fact, I'd enjoy this kind of weather until April. If the temperature is going to be cold, I'd prefer it to be very cold, because colder temperatures mean less trouble with icing.

Icing, the accumulation of ice on the airplane during flight, is a bigger problem than thunderstorms are. Thunderstorms are not as frequent in summer as icing is in winter, and thunderstorms are loud and boisterous, not stealthy like icing is. It is never a mystery where thunderstorms are, but icing problems can exist in a wide range of winter clouds. Most winter flight planning must consider altitude and routing which minimizes exposure to icing conditions.

Ice will form on the forward face of every part of the airplane's exterior almost any time that it flies through a cloud that is below 32 degrees. It collects on the leading edges of the wings and tail, on the propeller blades and around the engine air intake, and on the antennas, the landing gear, the windshield, and every little doo-dad that is protrudes from the plane. It cuts the efficiency of the wings, engine, and propeller while at the same time, adding weight and aerodynamic drag. It is 100% bad news because the aircraft requires more power when it is crusted with ice, but the ice reduces the power that the engine and propeller can deliver.

The good news is that all clouds are not created equal, and the sky is seldom filled with clouds at all levels. Clouds with a strong moisture feed, such as the ocean, the great lakes, or a strong south wind ahead of a cold front that stretches to the Gulf of Mexico can be a problem. Weather arriving directly from the west such as we have had for the last few weeks is little threat because it is colder and dryer than storms which swing up from the southwest.

Ice that remained on the wing of the Caravan after climbing through a layer of lake- effect clouds.

The problem of aircraft icing lays in the fact that the water within a cloud does not automatically freeze when the temperature drops below 32 degrees. It needs a bit of a nudge. Clouds at a temperature of 30 degrees will typically be composed of tiny drops of water, which are not inclined to freeze unless something like an airplane bumps into them. At this temperature, the water in a particularly moist cloud will strike the airplane and stream backwards on the wings and tail before it finally freezes. Ice such as this will build quickly, and will overwhelm the airplane's de-icing devices.

The atmosphere's ability to hold moisture decreases with temperature. As the temperature decreases, the cloud's moisture content drops, and the water droplets begin to freeze spontaneously. As more of the cloud's moisture freezes it becomes less of a threat. Any remaining water droplets freeze on contact with the plane and remain on the very leading edge of the wings and tail, where the accumulation can be managed with the deice systems. Somewhere between 15 and 5 degrees, the clouds become so dry, and the moisture so frozen that they can almost be ignored, just as though they were above 32 degrees.

The Cessna Caravan that I fly has been called an "ice magnet" because it is simple, boxy, and utilitarian rather than sleek and fast. It has landing gear, wing struts, and a large external baggage pod which are exposed to the slipstream and provide so many "extra" places for ice to collect. Adding insult to injury, the airplane is under powered compared to the multi-engine planes that are more typical of commercial service.

The plane had a full complement of deice devices however. There is a "hot plate" over part of the windshield which maintains a small area of ice- free viewing, there are heating pads at the roots of each propeller blade, and there are inflatable deice boots on the leading edges of the wings, tail, struts, and parts of the landing gear.

The windshield and propeller anti- ice systems are electrical resistance heaters, but the rubber deice boots are pneumatic. Air is bled from the engine compressor section and sent to chambers within the boots, causing them to puff up rapidly, and break the ice that has stuck to them.

Too cold for ice? Yes, there is such a thing. Once you are aware that clouds do not freeze until 10 degrees or so, and that cooler air can hold less moisture than warmer air, the concept is not hard to understand. It is closely related to the more familiar concept that it is "too cold for much snow to fall".


The author Bob Tilden flew a Caravan for a Night Express cargo company for 10 years and has also written a book, Gone Flyin', to order it, visit goneflyin.com or search Gone Flyin' on ebay.com

- CaravanPilot.com

Airframe icing and 600 lbs of excess weight led to C208B Caravan crash

Caravan C-GAGP operated by Gogal Air Services

On 18 November 2012 the Caravan pictured above crashed after loss of control due to an accumulation of Rime Ice on its wing surfaces. Accidents like this should serve as a reminder to us pilots that we need to be extra vigilant while operating in icing conditions. 

The Grand Caravan, operated by Gogal Air Services, was headed to Winnipeg when it crashed into a wooded area soon after take off. The crash killed the pilot and seriously injured the seven passengers on board. The 600lbs of excess weight and airframe ice increased the aircraft's stall speed and reduced its take off and climb performance.

According to the Canadian Transportation Safety Board:

"Although the pilot made an attempt to remove the ice before [the final] flight, a significant amount of it remained on the aircraft. No de-icing or anti-icing fluids were applied to the wing or horizontal stabilizer and no tactile inspection of the upper wing or tail surfaces was observed. The ice on the leading edges of aircraft's wings and tail would have reduced available lift, added extra weight, increased aerodynamic drag and thereby reduced its take-off and climb performance, increased its stall speed and impaired the protection afforded by its stall warning system, which is activated at a pre-set angle of attack based on a clean wing."

Caravan C-GAGP

After reading this, I encourage my readers to review the AFM or POH for the specific aircraft that they fly (difference between AFM and POH), specifically the sections pertaining to Icing and the Emergency Procedures - Icing. As far as the Caravan, you can also find this information in the Pilots' Abbreviated Checklist. But remember that the AFM or POH takes precedence over the PAC.

If you are a Caravan pilot, I also highly recommend that you complete some of Cessna's E-Learning courses on this topic. Courses such as "Caravan Cold Weather Ops" and "Caravan Vodcast Ground Icing Conditions". There are many other interesting courses available, most of which are free and are all available at cessnaelearning.com.

My fellow pilots, please remember to Review Often and Fly Safe so that you can continue to Have Fun!

- CaravanPilot.com