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Another Lufthansa Incident

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Another Lufthansa Incident

Old 8th Apr 2008, 12:35
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Another Lufthansa Incident

Apparently a Lufthansa Avro RJ 85 almost crashed on March 21st. German Newspapers are reporting about the incident



and here


The crew experienced an elevator control jam resulting in extrem pitch changes but managed to land the aircraft later safely.

The media are citing an internal Lufthansa report as evidence. The report says that most likely dried de-icing fluids have caused the control jam. Obviously some Lufthansa pilot passed the report and is complaining about insufficient maintenance at Lufthansa Cityline who are operating the Avros on behalf of Lufthansa.

Lufthansa are saying they are not responsible.

German authorities are saying that this is a known problem for several years.

Scary story. Any further information on that anyone?
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Old 9th Apr 2008, 06:32
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I don't know anything about the said incident but the problem with de-icing fluid in Avro's elevator system is very well known. Other operators have special procedures in place after having very similar problems, i.e. 2-step-de-icing and regular inspection. Type IV contains more thickener than type II, so if you use it the same way like II you get some very nasty solid residues inside the rudder/elevator.

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Old 9th Apr 2008, 06:54
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My company has operated 146 for years, and after a couple of de-icings ( Type IV not recommended) Techs completely clean the elevator.
This has not prevented 2 minor incidents we had last winter, one before take-off and one after but recoverable.

The 146/RJ family is very very susceptible to jammed elevators when having been deiced.
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Old 9th Apr 2008, 10:01
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Why the hell is this stuff approved for deicing then?

I have seen it oozing down the fuselage of the same type on stand at destination, at least 2 hours after it was applied at the other end, and after a rotation a flight and a landing of course. It is not supposed to be there.

I have watched it freeze at the end of flap mount fairings on 737 where I have presumed that it can cause no harm, and then watched it thaw again on decent.

It is unbelievable that so much cost and effort is expended by aviation designers and testers to avoid these things, but as soon as the certication is issued it becomes "one of those things" associated with very loose interpretation by groundrats, engineers and pilots alike, and drags on as such for decades all supported with notions like "yeah it's normal" or "well we've no evidence it has caused any accidents".
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Old 9th Apr 2008, 12:28
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slip and turn I'm totally with you! If situations like this are premitted to occur, eventually it'll cause a crash (or crashes), whether on this model or the same situation with a different plane. Although, the 146/RJ has been around since the 80s and this issue hasn't caused a crash prior to this.

There have been one or two incidents with flaps however, wonder if it's related?
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Old 9th Apr 2008, 14:21
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Seem to remember Fokker 100 was also prone to similar problems.
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Old 9th Apr 2008, 16:24
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March 2005

In March 2005, several European carriers flying the BAE146- / AVRO RJ-series encountered more or less during the same short time frame severe in-flight pitch disturbances and oscillations. Aircrafts of the Embraer 145- and LearJet-series have also been affected.

The effects on the flight control systems were:

1. With the AP engaged, slow cyclic pitch instability with a frequency of 0.1 Hz
2. Vertical speed indication changing
3. With AP OFF, a higher than normal control force required
4. Descending to warmer air, control forces required reduce to normal
5. Descending through precipitation and cold front, control forces remained high

The weather history before those incidents involved a long cold period with lot of de/anti-icing cycles followed by a dry period, and finally immediately followed by heavy precipitation and cold fronts.

The major root cause for those incidents was identified to be various residual forms of de-icing fluids in critical areas of the flight control systems.

As the industry seeks greater hold over times, thickening chemicals have been added to de-icing fluids leading to enhanced type II and type IV fluids. If these fluids are misused, i.e. incorrect application, failure to wash off previous fluids, over application or repeated application, then those fluids can remain in the gaps and “aerodynamic quite” areas in an airframe and leave potentially dangerous residues such as a dry white powder, sticky gel substances and thick lumpy balls. Exposing a de/anti-icing fluid to dry air for long periods (as is the case in flight) will see the evaporation of water and glycol from the fluid. This generally leaves the thickening agents and other chemicals in a dry powdery form. This dry powder residue, by itself, mostly does not cause any direct problem; although if enough were present on some external surfaces of some aircraft there could be severe aerodynamic effects. Dry residues on external surfaces are more easily cleaned during the course of daily operations, however, the dry residue that forms within the airframe will remain until such time it is detected and cleaned away. Often even when sought for, it can be difficult to detect. It is possible for many layers of dry residue to build up over a winter season. When these dry residues are exposed to moisture, such as rain or high humidity, the chemicals absorb the water/moisture and expand into a colourless gel-like substance. This gel residue can be many times greater in volume than the original fluid and dry powder residue. As this gel can form inside the aircraft before and during flight, and as the majority component is water; once the OAT falls below freezing the gel is likely to freeze.

Frozen gel can create flight safety problems in numerous ways. If the gel is frozen within the gaps between control surfaces, then certainly for non-powered control systems, these control surfaces may be difficult or impossible to move from the flight deck until the gel melts in warmer temperatures. Similarly, gel that freezes inside the airframe can interfere with control systems and have the same effect.

The March 2005 events highlighted to the industry that the residual de-ice fluid not only remained in the aerodynamic quite areas but has actually over the years managed to penetrate into the main elevator and tab structures. This required a new line of thought and changes to the way the residual inspection and cleaning of the aircraft has to be performed.
Subsequently, maintenance organizations (should) have changed their flight control inspection intervals and procedures significantly to prevent further de-icing fluid incidents.
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Old 15th Apr 2008, 11:33
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Thanks for the replies everyone. Looks like one is waiting for an accident to happen.
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Old 15th Apr 2008, 15:44
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The Embraer 135/145s are open to the same problem as the RJ. It's because of the elevator is not a hydraulic powered flight control. Best not forget the full and free check on line up then.
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Old 15th Apr 2008, 16:24
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As this is a known problem it is a concern that operators, particularly European Operators, are still experiencing serious incidents that may be due to re-hydration and freezing of thicked fluid residues. The CAA's winter operations FODCOM provides guidance on this matter and BAe has produced comprehensive information for opeartors.

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Old 15th Apr 2008, 16:26
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slip and turn,

Perhaps acquaintance with stuff such as Newtonian/Non-Newtonian fluid properties, boundary layers and other such sticky stuff, would lessen the outraged contrarian stance so often seen.

Besides, what colour is Type IV, or I and II for that matter.
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Old 15th Apr 2008, 17:50
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Pardon? Are you perchance calling my stance outraged and contrarian

The stuff I saw trickling down the fuselage of an RJ from somewhere around the wingmounts all the way down the sides was bluish green and after I pointed it out, the pilot told me what it was.

The stuff I saw on a 737 flap mount fairing wasn't in hugely noticeable quantities. I just found it interesting to watch its behaviour since I knew that after rotation it was not supposed to be there. It was a grey day so since I was peering through a grubby window, the colour could've been anything from bluish green through to pale yellow, but it didn't leave the wing on rotation and simply froze in the cruise and thawed on the way down.

PS I am not sure what is contrarian about my outrage on this occasion, other than that it may be a stronger view than that of some commentators who may be indifferent. However, I am sure the knowledge you describe might modify my view of the problem. Isn't knowledge like that somewhat beyond that possessed by most ATPLs who nevertheless have to make the decisions about what they allow to be sprayed on their airframe, how often, when and by whom?
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Old 15th Apr 2008, 18:37
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I'm not familiar with the 146/Avro line of aircraft. Are the elevators actuated directly or are they free floating (driven by servo tabs)?
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Old 15th Apr 2008, 18:42
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Very old news and by far not dramatic as it looks like!
Plane landed safely without any control problems at STR!
Plane was deiced around 10 hrs before the flight with Type 2!
Can' t go to much into details but the incident was not as critical as it was presented to the public!
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Old 15th Apr 2008, 20:32
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On the same day, an Air Dolomiti BAe 146 (I-ADJF) from Frankfurt made an emergency landing in Verona. The Italian AAIB preliminary press release says that the crew experienced some problems with the elevators because of ice.

Link (in Italian)
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Old 15th Apr 2008, 21:02
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wottsat “Looks like one is waiting for an accident to happen”.
This is a known hazard originating from:
  • excessive use of fluid – type 4 only requires a thin layer (1mm) to provide anti-icing (approx 1ltr/sq m), and / or
  • fluid dryout in gaps and crevices, or after (inappropriate?) overnight ‘defrosting’ spraying of fluid without wash off before flight, and
  • incorrect inspection/cleaning.
Type 4 fluid is dyed green

The BAe146/RJ uses servotab controls, the elevators are free floating.
A common point for the fluid residue to collect is in the servo tab or trim tab hinge gap at the rear of the elevator. Thus, the tabs can freeze, but the controls remain free.
Re #7 from CarbonBrake, a frozen trim tab is often indicated by (1 & 2) cyclic pitch oscillation. A frozen servo tab by (3), heavy controls; the control input is applied directly to the elevator – manual control.
Several aircraft suffer from these problems, notably those with manual controls / servo tabs. Other aircraft have reported associated problems, frozen spoiler / airbrake panels, or intermittent flap operation.

slip and turn “… that after rotation it was not supposed to be there.”
I believe that your understanding is incorrect. The industry, many years ago, accepted that approx 20% of de/anti-icing fluid would not be shed during take off. However, this was based on type 2 fluids and relatively high take-off speeds in a B737. Since then the industry uses the thicker type 4 fluids (higher viscosity) and the aircraft affected generally have slower take off speeds, this can result in the fluid remaining in ‘aerodynamically quite areas’ (gaps and crevices) as the airflow patterns change at rotation.
If excessive fluid is used, then the 20% remaining on the wing is 20% of too much, which in volume is more than the industry originally assumed; this further compounds the problem.
This is an issue of the industry requiring greater hold over times, but the solution not fully evaluated. Add to this poor practices and an organizational oversight that until recently (IIRC) no one held accountability for certification of the fluids.
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Old 16th Apr 2008, 02:23
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Seem to remember Fokker 100 was also prone to similar problems.
Same with the F28, as I recall.
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Old 17th Apr 2008, 08:43
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Is it just me or isn't that a problem that should be adressed by the authorities? I mean a lot of people seem to know about but still there are such dangerous incidents happening.

I don't know about the Air Dolomiti flight aerolearner mentioned but the german media covering the LH incident were publishing an official LH report about it here


and I am happy I haven't been on that flight. The controls were stuck for quite some time and the crew were expiriencing vertical speeds between -200 and + 5300 ft/min during the encounter. That was a very serious incident.

How can that still happen when the problem is well known!

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Old 17th Apr 2008, 20:27
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New developments

Just a little update on what's happening over here: According to today's news reports, a preliminary report form BFU (the federal agency investigating aviation incidents) states that insufficient de-icing of the aircraft caused the problems leading to an emergency landing. The aircraft's elevators had not been blocked by dried de-icing fluids, as indicated by earlier reports, but by iced snow or "graupel", as lab tests had shown. (Does this word really exist in English, as my dictionary suggests? It's "Graupel" in German. Soft hail, if you prefer). "In hindsight, the pilot's decision to not de-ice the Avro that day, was not optimal", a BFU official is quoted.

The news report concludes that the new findings don't point to general maintenance problems at Lufthansa City Line as a cause for this incident. Earlier news stories citing an internal Lufthansa report had suggested that, as was discussed here. After the new BFU findings had been publishd today, German TV station ARD pulled an investigative report on maintenance issues that was scheduled for tonight.

The BFU report acknowledges that dried de-icing fluids are a known issue with this type of aircraft, though. Residues of fluid can accumulate on elevators and ailerons easier on this type of plane, the BFU reportedly said. This had caused some emergency landings in 2005. Since then, maintenance procedures had been adjusted appropriately. The BFU says not knowing about related incidents with Lufthansa aircraft since 2005.

A Lufthansa spokesman didn't want to comment for the article, saying the company would wait for the final BFU report.
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Old 17th Apr 2008, 21:28
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Yes graupel exists in english though I hadn't come across it before I started flying.
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