Why are modern jet tails not de-iced(in flight)?
Capt Claret
That has been my experience, too. It was crazy, on the B727, to ask if the Captain wanted anti-ice on and get back, "oh, we don't need it." Like it cost him or the company money!! My best comeback was, "it's free!"
GF
That has been my experience, too. It was crazy, on the B727, to ask if the Captain wanted anti-ice on and get back, "oh, we don't need it." Like it cost him or the company money!! My best comeback was, "it's free!"
GF
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To answer the comment about a "bow wave" effect shielding components from ice accretion.
There can be an element of this present, and it would be particularly noticeable for fuselage mounted antennae, for example. But it's simply not a large enough effect to shield the tailplane. (Consider the fact that engine anti-ice is routinely fitted to aircraft with aft-mounted engines).
Additionally, the inflight evidence is clear - ice does accrete on virtually any surface in the airflow. The key for the aircraft with no tail de/anti-ice capability is, as stated before, that they are DESIGNED with that consideration in mind. It's a tradeoff between the complexity (and weight) of another de/anti-ice system, versus the cost and weight of an otherwise oversized tail surface. Generally the latter tends to be the better compromise.
I can't find any of our icing pics in the public domain right now, but NASA has some impressive pictures in their icing training.
The following quote is from intro #2 of their In-Flight Icing Training
I think that's fairly conclusive in showing that tailplanes of large swept wing types can, and do, accumulate ice.
There can be an element of this present, and it would be particularly noticeable for fuselage mounted antennae, for example. But it's simply not a large enough effect to shield the tailplane. (Consider the fact that engine anti-ice is routinely fitted to aircraft with aft-mounted engines).
Additionally, the inflight evidence is clear - ice does accrete on virtually any surface in the airflow. The key for the aircraft with no tail de/anti-ice capability is, as stated before, that they are DESIGNED with that consideration in mind. It's a tradeoff between the complexity (and weight) of another de/anti-ice system, versus the cost and weight of an otherwise oversized tail surface. Generally the latter tends to be the better compromise.
I can't find any of our icing pics in the public domain right now, but NASA has some impressive pictures in their icing training.
The following quote is from intro #2 of their In-Flight Icing Training
Originally Posted by DC-10 pilot
As we arrived at the gate, I noticed that all the mechanics were standing off to the side, pointing at something in the back of the airplane. After the people got off, we went to the rear of the airplane and noticed there was about eleven inches of ice on the horizontal stabilizer.
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So...you heavy jet operators that almost never have used wing anti ice, what is the Airbus/Boeing requirement to use it? Do they say to wait until ice is observed on the wing first, and then turn it on?
Light jets seem to have a temperature requirement to have wing (and engine) anti ice on, if in cloud or visibility is less than 2 miles.
Light jets seem to have a temperature requirement to have wing (and engine) anti ice on, if in cloud or visibility is less than 2 miles.
Bottums Up
Can't see it from the 717 cockpit. And with security requirements, I wonder if I can dispatch the F/O in flight to look out the pax window! 
Even less to see at night. 
Even less to see at night.
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Many moons ago I was paxing aboard Braniff's then sole B747-127, the orange "pumpkin" N601BN, LGW-DFW. During descent I had noticed a rapid build-up of about 2 inches of ice on the entire leading edge, but in less than a minute it had all disappeared as we had obviously transitioned into a warmer air mass.
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Don't train yourself too much on the NASA videos without understanding your type. This came up recently in the Colgan crash. NTSB report:
The NTSB notes that, at the public hearing for this accident, a Bombardier engineering manager testified that the Q400 was not susceptible to tailplane stalls. The Bombardier official described the flight testing—the 0 G pushover maneuver—that was performed by Bombardier and Transport Canada to make this determination. The Bombardier engineer explained that the maneuver, which was conducted with ice accumulation on the airplane’s tail (with both natural icing conditions and artificial ice shapes), involved pushing the control column forward to lower the nose of the airplane and increase the airplane’s descent rate. The Bombardier engineer further stated that this maneuver tested “the most severe condition” (that is, the most negative tailplane AOA) and that the airplane showed no evidence of tailplane stall characteristics, even at -0.2 G.
later
Also during public hearing testimony, the FAA’s manager of air carrier training stated his belief that no airplanes currently being operated by Part 121 air carriers were susceptible to tailplane stalls. He recalled that the early versions of two airplanes, the Saab 340 and the Jetstream J31, had tailplane stall tendencies but stated that these tendencies were corrected by airworthiness directives and manufacturing changes. The FAA manager further indicated that training programs should not lead to negative training or possible miscues regarding how flight crews are to handle a full wing stall.
The NTSB notes that, at the public hearing for this accident, a Bombardier engineering manager testified that the Q400 was not susceptible to tailplane stalls. The Bombardier official described the flight testing—the 0 G pushover maneuver—that was performed by Bombardier and Transport Canada to make this determination. The Bombardier engineer explained that the maneuver, which was conducted with ice accumulation on the airplane’s tail (with both natural icing conditions and artificial ice shapes), involved pushing the control column forward to lower the nose of the airplane and increase the airplane’s descent rate. The Bombardier engineer further stated that this maneuver tested “the most severe condition” (that is, the most negative tailplane AOA) and that the airplane showed no evidence of tailplane stall characteristics, even at -0.2 G.
later
Also during public hearing testimony, the FAA’s manager of air carrier training stated his belief that no airplanes currently being operated by Part 121 air carriers were susceptible to tailplane stalls. He recalled that the early versions of two airplanes, the Saab 340 and the Jetstream J31, had tailplane stall tendencies but stated that these tendencies were corrected by airworthiness directives and manufacturing changes. The FAA manager further indicated that training programs should not lead to negative training or possible miscues regarding how flight crews are to handle a full wing stall.
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I have been reading this fine thread and I have noted some commentary on the DC-9 / MD-80 and B717 series and tail icing.
What may not have been discussed is the fact that the pilot does not have normal direct control over the elevator on these aircraft. He is controlling a servo tab that is connected to the elevator. Only in an extreme nose down push is a hydraulic actuator directly tied to the control yoke and the elevator. This is a last ditch pitch contol system in the case of deep stall.
If you consider all the various weird shapes that could accrue on a tail surface in heavy icing you can visualize that laminar disruption by a horn shape could render the servo tab almost useless. With an ineffective servo tab elevator control is greatly reduced or even eliminated.
I have experienced elevator / pitch control degredation in the DC-9. We were holding for KROC, Rochester NY, in a heavy snowfall. The icing was very heavy and you could see the auto pilot, which is pretty crude in the Diesel 9 anyway, become more and more ineffective. We got out of the WX and activated the tail anti-ice and things firmed up quickly.
What may be reported as tail stall or some other phonenomen may actually be simply loss of contol effectiveness due to the servo design of the DC-9 series.
The aircraft is very reliable once you understand that you have to keep the tail clean. Even more than the wing.
What may not have been discussed is the fact that the pilot does not have normal direct control over the elevator on these aircraft. He is controlling a servo tab that is connected to the elevator. Only in an extreme nose down push is a hydraulic actuator directly tied to the control yoke and the elevator. This is a last ditch pitch contol system in the case of deep stall.
If you consider all the various weird shapes that could accrue on a tail surface in heavy icing you can visualize that laminar disruption by a horn shape could render the servo tab almost useless. With an ineffective servo tab elevator control is greatly reduced or even eliminated.
I have experienced elevator / pitch control degredation in the DC-9. We were holding for KROC, Rochester NY, in a heavy snowfall. The icing was very heavy and you could see the auto pilot, which is pretty crude in the Diesel 9 anyway, become more and more ineffective. We got out of the WX and activated the tail anti-ice and things firmed up quickly.
What may be reported as tail stall or some other phonenomen may actually be simply loss of contol effectiveness due to the servo design of the DC-9 series.
The aircraft is very reliable once you understand that you have to keep the tail clean. Even more than the wing.
