SmoothOnTop

CRJ?

Bombardier completed in flight icing tests and transport canada and the faa determined the CRJ did not require stab/tail fin anti icing.

Why exactly does the tail pick up more ice?

The sharper (or pointy - er) the surface, the more ice accretion.

Today's pneumatic boots don't need a build-up before they can effectively remove the ice.

If you see ice, blow the boots frequently (especially before configuration or speed changes) or put them in auto if it's available...

SebastianDesoto

I am having a problem understanding the issue of power and its effects on tail stall. I have looked over this video a couple times.

I will figure that out eventually. Beyond that,however, the part that really concerns me is the tail stall is recovery, especially in context of approach to landing.

1. pull back on the yoke
2. reduce flap setting
3. "judicious with power"

It would seem that during an approach, a missed approach/go-around would follow a tail stall recovery. It would certainly put you out of a stabilized approach.

The first two procedures are similar to go-around proceedures anyway, except that adding power is usually the first thing to occur or simultaneous with initiating a climb. If power is added during this critical moment, and induces a secondary tail stall (which I am still unclear how this happens), then actual missed approach procedures could not follow.

What happens now? Do I just tell tower I think we might have induced a tail stall and need to fly around at level slow flight for a while? My brain is racked

iPilot

Hey dash 8 guys, does the Q400 have automatic ice systems like most RJ's? I flew the ERJ and it just worked whenever ice was detected. From what I heard from some King Air folks at least, even the new ones have to be manually acuated. The old rule of thumb was to wait until you got a nice amount of icing before activating the boots but now apparently that's not the case. Anyway, my point is the NTSB said 3407 had its icing system activated during the accident. Does that mean the boots are running or that its simply waiting for the computer to decide when its in icing?

fboehm

Ice will accrete more rapidly on a narow profile.

If an aircraft has reversible controls, there will likely be a pressure change over the elevator during the tail stall event and the yoke will be taken to the forward stop. You have to pull the yoke back to correct. You would also want to retract the flaps and reduce power.

The Dude Abides

The boots are not activated automatically, you have to select them on. There are 3 settings; slow, fast and manual. In slow or fast the boots are cycled automatically. Can't remember the dwell times.

KC10 FATboy

The video posted above is what we watched. I was wrong in my post about what NASA actually did, but, its the same video. If you don't get it after watching that video, you never will. The video is excellent.

I think the takeaway is ..

-Don't use autopilot during icing conditions as it might mask a tailplane ice stall situation
-Higher power, speed will worsen the situation. Apply power judiciously and maintain precise airspeed
-Avoid high flap settings in icing (if possible), if not, give yourself plenty of altitude for recovery
-Make pitch chages slowly. If you have any difficulties trimming, lightening of the controls, you may be enterring a tailplane stall.
-Use anti-ice systems.
-Recovery usually means raising the nose, reducing flaps, and reducing power.

-Fatty

fboehm

Here are some references regarding ice and ICTS events that I found interesting. I have not most of it should still be retrievable.


George, F. (2003, January). Giving ice the boot [Electronic version]. Business &
Commercial Aviation, 92 (1), 58

Horne, T. A. (1994, March). Tailplane icing [Electronic version]. AOPA Pilot.

Horne, T. A. (2000, October). Winter weathers worst [Electronic version]. AOPA Pilot.

Horne, T. A. 2003, (November). Iced up tails. AOPA Pilot, pp. 155-59.

National Transportation Safety Board. (1992, October). DCAMA001. Retrieved [11-
15-2003] from [National Transportation Safety Board http://www.ntsb.gov]


National Transportation Safety Board. (October, 1996). DCA95MA001. Retrieved[11-
08-2003] From [National Transportation Safety Board http://www.ntsb.gov]

Ratvasky, T. P., Van Zante, J. F., & Riley, J. T. (1999, January). NASA/FAA Tailplane
Icing Program Overview. Springfield, VA: National Technical Information
Service.

U.S. Department of Transportation. Federal Aviation Administration. (2001,
December). AC No: 23.143-1. Ice Contaminated Tailplane Stall. Retrieved [11-07-2003] from [Federal Aviation Administration http://www.faa.gov]

UAL T38 Phlyer

In every airplane I know of (except the Stearman and the F-16), the horizontal stabilizer provides down-force to hold the nose up, as the c.g. is forward of the center of lift.

Normally this force is only about 5% or so of the total lift provided by the wings. If the wings are lifting an airplane that weighs 100,000 lbs, the wings must lift 105,000 lbs, and the tail "pushes down" 5,000 lbs. Net result: steady-state flight (no nose movement up or down).

When flaps are extended, there is a significant downwash change. In other words, the air no longer streams straight back from the wing---it is "deflected" downward. As this downwash increasingly impacts the top-surface of the Horizontal, it would normally tend to increase the down-force--which would normally make you pitch-up.

However, this may be offset by the nose-down moment caused by extending flaps. In every airplane I've flown, a significant amount of nose-up trim (ie, increased tail down-force) is required as the flaps are extended.

In a T-tail design, the increased downwash--which normally somewhat compensates for the nose-down moment of extending flaps--is removed, because the horizontal is high enough it is not affected by the downwash. This means you must compensate by pulling back on the stick, or trimming the entire Horizontal (on aircraft so equipped, such as jets).

If only pulling-back on the stick, you may achieve a point where the elevator cannot provide sufficient force to overcome the nose-down pitching moment of the flaps, OR, the elevator itself may stall.

In the Lear family (20s and 30s), even with a trimmable Horizontal, there may not be enough force available, and if heavy ice was confirmed, or tail ice suspected, you were supposed to land flaps-up or minimal flap.

And the Lear 35 has heated emmpenage.

As to why the tail may or may not develop more ice: I've never heard the pointy-er, the more ice. I would have believed just the opposite. The boundary layer increases in depth from nose to tail of fuselage, or leading to trailing edge of surfaces.

Boundary-layer air is air that "isn't moving as fast as the free-stream." For air to slow down, it usually expands, then slows. When air expands, it cools off, and increases the likelhood any remaining mosture will be deposited as ice.

Last idea on the topic: perhaps the CRJ, with swept wings, benefits from spanwise flow. That is, "downwash" in the horizontal sense. Except in supersonic flow, air going over a swept-wing "bends" and tries to flow slightly outboard. This spanwise flow causes AOA to be "apparently" higher at the wingtips, and will cause tip-stall first, unless the wing has reflexive-twist or aerodynamic washout.

So, if the flow is moving away from the fuselage due to wing-sweep, it may carry the bulk of the moisture-laden air that would cause ice with it.

Luckydawg

This is where your PIC authority comes into play. This scenario happened to a co-worker of mine around 1998 or 99 in STL. They were configuring for a landing during an ILS and just selected final flaps. The tail stalled, they recovered with your 1,2,3 steps above. In the process they lost about 400 feet. This sent bells and whistles to the tower. Tower told them to go around. They declared an emergency, reintercepted the glideslope and landed. You don't get a simplified answer for all scenarios, this could happen in different phases of flight but IMHO it will happen most likely when slowing, configuring for an approach.

captain152

All excellent posts. Thanks to everyone for sharing their info.