Icing in FS9

[Tom Goodrick]

For a challenge, we should create some cases where we will encounter icing and have to deal with it. In FS9 the only way to do this is to make your own weather. This time of year in the US, conditions favorable to ice development occur on just about every flight in Real Weather. But if you fly those conditions in FS9 you will encounter no ice. You can land in heavy snow or freezing rain and encounter no ice. That is just the way they made FS9 - not quite as real as it gets.

But when you use Advanced Weather to build your own conditions, you can turn on icing. For realism, put your icing level in clouds where the temperature is between 28 and 35 degrees F. You can choose light, moderate and severe icing levels.

One difficulty I have is setting this up as a local event so you can go to a moderately distant airport and find good weather. In trials years ago, I escaped icing near Chicago, fly to Alabama, and found the exact same icing conditions there when I made my approach.

You will see icing in two ways: 1) pitot tube ice will shut off your airspeed. 2) airframe ice will increase your "dry" weight. The second effect can knock you out of the air. You may reach a condition, well over gross, where you cannot climb at all forcing you to stay in the icing and eventually to descend no matter what you do.

Recently a small plane pilot reported icing was causing his plane to lose power and to descend into mountains. His plane was found in the side of a mountain. This may have been more of a result of airframe icing than of an effect of ice on his engine. When P/W gets low, you lose altitude, regardless of whether P is getting low or W is getting high. Another effect of icing that we do not have in FS9 is deformation of the lifting and control surfaces. That more commonly gets jets that need clean wings to fly.

I'll be building an icing condition. I'll let you know when it can be shared. Meanwhile, why don't you try?

I had an ICE gauge on my web site. If you missed it, just send me an email. It shows how many pounds your weight has increased due to ice.

[louross]

Aircraft icing.
Weight problems? Minimal. Ice weight compared to a/c is negligible.
Icing problems: distortion of airflow over the wing and loss of propeller thrust.
The accident reports are filled with examples of light plane accidents (props) due to a thin layer of ice on the wings.
lr.

[Tom Goodrick]

It is not clear that the weight effect is actually minimal. The skin area of an aircraft can be significant. When an aircraft takes off at max gross weight, any weight is added to that (less fuel burn). The DC-3 is an example of an aircraft that has a lot of wing area and fuselage area that climbs slowly and can pick up a good load of ice.

I agree that in many cases, though, the cause of an accident is airfoil distortion on the wing and/or tail surfaces. That can happen with only a thin coating of ice.

In FS9, the only way to detect icing is by looking at the gain in dry weight. You can also notice when the airspeed drops to zero. But that happens when ice is first encountered, long before any flight problems occur. Flipping the pitot icing switch ON cures that problem but does not fix the developing flight problem. The gain in weight is simply a measure of the amount of icing. It does not predict aircraft behavior.

My flights yesterday indicated to me that there is probably more of an effect in FS than just the weight. I created an icing condition at Harrisburg International (KMDT) that extended, in a moderate snow storm, to 7200 ft (essentially over at 5000 ft).

The Cessna 182 starting at 2989 lb) was overwhelmed and unable to maintain altitude at 4000 ft with 70 lb of ice. I returned to the airport and landed okay with 69 lb of ice. The cause of the inability to maintain altitude at full power setting seemed more likely degraded aerodynamics. I used the autopilot in the climb but manual control coming back to the airport.

The Cessna 182 RG (starting at 3099 lb) was still climbing 800 fpm at 3000 ft when airspeed of 120 kias started dropping. At 4500 ft airspeed was 100 kias, at 5500 ft it was 90 kias and there was 20 lb of ice. At 6000 ft airspeed was 60 kias and there was no climb. I turned back. I was able to maintain good airspeed and a slight descent rate back to the airport.

With the Piper Cherokee 6 (3573 lb at start), I screwed up on the first flight (with autopilot) by forgetting about pitot heat. When I found I had trouble, there was no airspeed. I thought I turned on the heat but hit the wrong switch. The autopilot should have been turned off before it stalled the plane and went into a spin (zero visibility). I crashed. The second time I used the autopilot only for heading control and made sure the pitot heat was on before takeoff. I leveled at 5000 ft with 40 lbs of ice and only 88% max power holding at 118 kias. I was able to complete the flight to BWI and land safely. The ice dissipated during the descent near BWI. The solution here was to avoid using the autopilot for altitude control. Set trim manually in icing. The autopilot, when unable to maintain the set climb rate, will run the trim to max nose-up. Any climb rate is acceptable in icing unless the plane becomes overwhelmed.

[Tom Goodrick]

I flew the Bonanza V35B through the ice and on to cruise at 8,000 ft. There was only 25 lb of ice. I forgot the pitot heat but kept the plane flying until the airspeed was visible. I used the autopilot only for direction control.

[Tom Goodrick]

Today, I found an easy way to get into icing conditions in FS9. Load "Winter Wonderland" from the Weather menu and go for a flight. It will be more intersting if you take along an ice gauge. It is not severe icing, more like light to moderate icing. But it does happen from zero to 5000 ft. I suspect "Heavy Snows" will also have some ice.

I flew a Cessna 340 around for a while at 5000 ft and picked up 20 lbs of ice but had not trouble. You can detect ice by losing airspeed. Turn on pitot heat and it will come back.

I flew a Skylane from takeoff to 7000 ft and only picked up a few pounds that dissipated as I cruised at 7000 ft.

[Tom Goodrick]

Yesterday I investigated the default "Heavy Snows" weather case in more detail than before. It should be very bad for icing, worse than the "Winter Wonderland" case. But it only has ice in a narrow vertical band - 4500 ft to 6500 ft. And that is only in localized areas that move. As I flew around within 20 nm of KHSV, I picked up ice but only about 10 lbs on the Baron and it dissipated as I flew into a warmer area at the same level.

The wind was a little challenging (11 nm from 40 degrees) but each of several approaches to 36R was different. In some cases blinding snow held through touchdown. In other cases the snow vanished as I passed over the threshold or just before.