CT airframe in IMC physical Limitations?

[Skunkworks85]

There has been many discussion on if you can legally fly a CT into IMC, I think that point has been beaten to death. 

It generally concludes with you can equip the aircraft with the proper instruments and documentation to be able to fly on an IFR flight plan, but would not be recommended to fly into actual IMC.

 I do not have any experience in flying IMC, I would like to understand what PHYSICAL limitations that exist that leads to the conclusion of IMC is not recommended.

1. Icing? - Other IFR a/c do not have issues

2. Static Build up? - There was talk about arcing in the gear boxes of the 912. is this really a thing? I suspect it is not.

3. others?

 

Let me know your thoughts.

 

 

[Tom Baker]

I know before the change in 2010 to prohibit flight in IMC there was a fellow flying a CTSW who declared and emergency in a IFR flight plan when the engine quit. He was in IMC, and the suffered fuel starvation from the fuel vents icing over. He may have had this happen twice. That was part of what led to the change.

[Skunkworks85]

Do you think there is something to the design of the CTSW vent that makes it susceptible to icing? or would that have happened in a Cessna 152 as well? 

The LS has different vents correct? 

[Tom Baker]

It could have happened on anything. Ice forms first of protrusions, like on the old style OAT gauge sticking through the window. The vents on the CTSW stick up there just to collect ice. Yes the CTLS has a different style vent.

[frfly172]

I fly a liberty xl2 which is mostly composite ,it will handle light IMC and rain. Ice is one of the reasons not to fly most airplanes IMC. Rain is a major problem if you are running a composite prop.

[Jim Meade]

Aircraft approved to fly in IMC have different issues with ice.  Some aircraft are approved FIKI (flight into known ice).  Others are approved for IMC but not into known ice and if they encounter ice should get out of it.  An airplane that is not FIKI may not legally file a flight plan that would lead it through known ice.

Aircraft that expect to fly in weather that may support icing are likely to have heated propellers, heated windshield or a heated panel, heated pitot tube, and a way to shed ice from leading edges such as the wings and stabilizer.  That may be boots, heated leading edge, weeping wings and so forth.

 

[Skunkworks85]

8 hours ago, Jim Meade said:

Aircraft approved to fly in IMC have different issues with ice.  Some aircraft are approved FIKI (flight into known ice).  Others are approved for IMC but not into known ice and if they encounter ice should get out of it.  An airplane that is not FIKI may not legally file a flight plan that would lead it through known ice.

Aircraft that expect to fly in weather that may support icing are likely to have heated propellers, heated windshield or a heated panel, heated pitot tube, and a way to shed ice from leading edges such as the wings and stabilizer.  That may be boots, heated leading edge, weeping wings and so forth.

 

I understand FIKI,

Maybe I should rephrase the question. What physically allows say, a 152/172 to fly IMC that a CT is missing, This is from an airframe perspective. Lets assume you add heated pitot to the CT. Other than that, what are we missing?

 

[Tom Baker]

Lightning protection.

 

[Jim Meade]

91.205(d) prescribes the requirements for IMC flight.  None of the items I listed in my post are required for legal IMC flight, including heated pitot.  They are simply useful to deal with exigencies that are likely to arise in ice, which is more likely in clouds.

If aircraft are equipped per 91.205(d) there is no reason I know of it can't physically fly IMC .  I don't know of a lightning protection requirement for slower aircraft, but I am not an authority on that.

 

[GrassStripFlyBoy]

I've been thinking of going for IFR rating now that I have an airplane equipped to train with, I'd also consider actually flying in very light IFR, call it marginal VFR and no significant weather risks, summer time easy stuff - very select days with extremely short elements of true IMC..  Sure, there are some real points to consider when looking at CT's for these missions, but I'll say I'd much rather be in a CT with chute, than a 182 without one.  

[Skunkworks85]

22 hours ago, Tom Baker said:

Lightning protection.

 

What would need to be added to the ct to make it have lighting protection?

[Tom Baker]

53 minutes ago, Skunkworks85 said:

What would need to be added to the ct to make it have lighting protection?

A conductive mesh bonded into the composite structure. That is the typical method for a composite aircraft.

https://www.compositesworld.com/articles/lightning-strike-protection-strategies-for-composite-aircraft

[frfly172]

Rotax when they first came on the scene did not have carb heat so IMC was not authorized . They have since come out with a 912 that can handle IMC.

[ct9000]

Without wanting to complicate the discussion IMC does not just mean cloud. IMC means that the visibility has reduced to below legal minimums and may mean smoke or dust etc.

[Skunkworks85]

On 12/23/2020 at 7:28 AM, Tom Baker said:

A conductive mesh bonded into the composite structure. That is the typical method for a composite aircraft.

https://www.compositesworld.com/articles/lightning-strike-protection-strategies-for-composite-aircraft

Tom, what major reservations would you have about flying this airframe in light IMC? 

[oceanplexian]

I experienced something resembling inadvertent IMC (Visible precip @ about 10 degrees OAT) in the -SW a long time ago. I lost the pitot and airspeed indicator after 1-2 minutes, no visible ice accumulation on the airframe or wing, airspeed indicator froze at 110kts regardless of power changes. I executed a 180 and got out of it, flew to a nearby airport where and landed then confirmed a big chunk of ice in the pitot. 

Now I am a lot more conservative but my take away is the pitot would immediately be a problem.

[frfly172]

Carb heat and a heated pitot and then the radios for IFR would probably handle light IFR,IMC. Can be frustrating when you can’t pop up through some light clouds and marginal VFR conditions.

[andyb]

3 hours ago, frfly172 said:

Carb heat and a heated pitot and then the radios for IFR would probably handle light IFR,IMC. Can be frustrating when you can’t pop up through some light clouds and marginal VFR conditions.

Problem is it's very difficult to know if the IMC you're entering is light or not.

[Madhatter]

I used to own a 1947 V tail bonanza years ago which did not have a heated pitot. I flew it IFR for years with no issues summer and winter. It just takes some planning and common sense. Most ga aircraft have no business being near ice and I have always avoided it. I know too many that tickled that dragon's tail and it's not worth it.

[Skunkworks85]

10 minutes ago, Madhatter said:

I used to own a 1947 V tail bonanza years ago which did not have a heated pitot. I flew it IFR for years with no issues summer and winter. It just takes some planning and common sense. Most ga aircraft have no business being near ice and I have always avoided it. I know too many that tickled that dragon's tail and it's not worth it.

What happens to the dynon boom style pitots when water gets in them? Is there anyway to add a drain to the system?

 

[Madhatter]

Yes there is, I added a drain system also to protect my dual  Garmin air data computers.

[Jim Meade]

From personal experience, flying with a windscreen iced over and opaque is not fun.  Even a slip may then expose the side to ice.  Even a good defroster may not be enough so that one wants a hot plate or heated windscreen of some kind.