MD80 performance penalties from de-/anti-icing fluids

[Knold]

Hi all,

This is probably more operational than technical but it's the only place I found to stick it in so here goes:

I've been rumaging through AFMs, FCOMs and OMBs for days now without finding anything on potential performance penalties from de and anti icing fluids.
I know other aircraft types have this and I susspect the MD would too. However, I'm not sure if there has been any testing done on it.

Any of you folks out there with any experience or knowledge of this? MDC/Boeing directives or company developed info, anything at all!

Cheers!
Knold

[BOAC]

All I can tell you is that on the 737-200 BA used to knock 5 off the assumed after de-icing. I think this was dropped on the 3/4/5. At the moment, in my present company, we do NOT reduce at all following de-ice.

There has always been the suggestion that the film of fluid adversly affects the surfaces.

[Knold]

Rumor has it that the MD is especially vaulnerable to type IV fluid. Supposedly it may enter into the elevator hinges or wossname and clog it until it suddenly loosens and can make for a very interesting rotation.

I called Boeings Douglas product support but they want a fax and told me "we'll get back to you". I was hoping for some quicker response.

[mutt]

MD90 Company policy restricting reduced thrust but no other penalties.


Mutt.

[Knold]

By which formula?

Thanks!

[bafanguy]

knold,

We also had a restriction on use of flex power in the case where anti/deice fluids had been applied and OAT is +6C or below. There was no reference to the type of fluid.

I don't see any mention in the manuals of a reason for this. I've never thought about why, it was just one of a list of cases where flex power was prohibited.

But, now that you mention it, I'd be curious to know.

[alatriste]

According All Operator Letter AOL C1-E60-HHK-89-L038 issued by Douglas on January 19,1989:

# When OAT is at or below 6ºC and fluids have been applied, the use of derated thrust is recomended only when the assumed temperature and associated takeoff speeds are determined based on an Equivalent Weight which is 5% above the ATOW.

# When OAT is above 6ºC , standard derated thrust procedures can be be used if desired.



REGARDS.

[bafanguy]

alatriste,

Does the letter say "why" ?

[Knold]

Thanks for you reply alatriste,

So in a sense what is says is if you have an actual TOW of 63t
you should calculate the performance for a weight of 66.2t (66.15)?!

What if your actual is already at max? 72.5t. Then what?
(Probably not alot of flex left in the engines but anyway).

So, is this document still valid or was it lost in the Boeing merger?

Also, if one wanted to be a stickler for word interpretation. The only "real" derating on the MD is the ART system.
The assumed temperature is not a derate in itself, or so I was told by a performance engineer. But I'm sure that was not what MDC meant.

[alatriste]

Reason for OTOW penalty according AOL C-1-QNW-MGB-89_L592

dated December 21,1989.

" At temperatures below 6ºC the fluids may not completely flow off the wing by lift off, and this can result in a small increase in drag and/or reduction in maximum lift."

Beside that, I think that AOL recomendations concerning penalties, no longer aplies cause of right now deicing fluids approved by the AEA must comply with fluid´s flowoff characteristics test criteria.

REGARDS.

[bafanguy]

alatriste,

Thanks you very much for the info.

[Knold]

Thank you alatriste,

so I assume the caracteristics of the type IV fluid has been changed since this remmomendation was issued, correct?

[alatriste]

As far as I know type IV fluids were introduced in 1994.

REGARDS

[hawk37]

1. Are there aircraft out there that the Flight manual specifically says that type 4 is not permitted?

2. Any aircraft where type 4 is permitted based on certain additional operating requirements?
I'm not referring to the use of derated power mentioned above, but perhaps a minimum V rotate, or additives to V rotate or V2?

Hawk

[Shore Guy]

From a Boeing document at this link:

http://www.boeing.com/commercial/aeromagazine/aero_08/deice_textonly.html


TYPE II AND TYPE IV FLUID REHYDRATION AND FREEZING
Last winter in Europe, restricted elevator movement interrupted the flight of two MD-80 airplanes. In both cases frozen contamination, a gel with a high freezing point, caused the restricted movement. The gel was Type IV fluid residue that rehydrated during takeoff or climbout in rain.

Rehydration can occur when thickened fluid is repeatedly applied in dry conditions, either to prevent frost from forming overnight or for deicing just before flight. The fluid dries out during flight, and a powderlike residue remains in aerodynamically quiet areas, such as balance bays and wing and stabilizer rear spars. If the airplane is not deiced or anti-iced during a subsequent layover and encounters rain on the ground or during climb, the remaining residue absorbs water and turns into a gel. The gel swells to many times its original size and can freeze during the next flight leg, potentially restricting the movement of flight control surfaces.

In the case of both MD-80s, the frozen gel restricted movement of the elevators, which are unpowered flight control surfaces on that model. Both flights were diverted, and elevator movement was restored when the gel unfroze during descent as the airplanes encountered warmer temperatures at lower altitudes. Inspection after the return of one of these flights revealed gel in the area between the elevator and elevator control tabs.

The issue of rehydration was discussed at the Society of Automotive Engineers (SAE) G-12 Fluids subcommittee meeting last May. The subcommittee also discussed related occurrences on other types of airplanes with unpowered flight controls and the deicing/anti-icing procedures used by the operators attending the meeting. These discussions led the subcommittee to conclude that the residue builds up when a one- or two-step deicing/anti-icing procedure is followed using Type II fluid, Type IV fluid, or both, in either neat or diluted form. This practice is prevalent in Europe.

The SAE G-12 Fluids subcommittee recommended including a caution note in the next revision of SAE ARP 4737 to address this issue. The SAE G-12 Methods subcommittee agreed and is including the following note in SAE ARP 4737D, scheduled to be released in late 1999.

CAUTION: The repeated application of Type II or Type IV, without the subsequent application of Type I or hot water, may cause a residue to collect in aerodynamically quiet areas. This residue may rehydrate and freeze under certain temperature, high humidity and/or rain conditions. This residue may block or impede critical flight control systems. This residue may require removal.

This caution note is similar to Precaution Note Number (6) of the MD-80 Aircraft Maintenance Manual (12-30-01):

After prolonged periods of deicing/anti-icing, it is advisable to check aerodynamically quiet areas and cavities, like balance bays and rear spars of wing and stabilizer, for residue of thickened fluids.

Boeing will address these issues in a service letter to be released in late 1999.

[Knold]

Thank you all for your help, very appreciated

Cheers

[alf5071h]

Knold, re your so I assume the characteristics of the type IV fluid has been changed since this recommendation was issued, correct? It is always a danger to assume anything in aviation. I do not know of any specific changes in the specification, but there could have been a tightening of the testing of fluids against the specification or additions to the specification to clarify the problems of dry out. However many problems remain such as the fluid characteristics when ‘contaminated’ with precipitation during hold over; I understand that the Canadian DoT has done some testing in this area. Similarly there could be problems if the fluid is over applied; a very thick layer may not shear off the tail / wing or fall into in the tailplane/ elevator / servo control tab gap, leading to aerodynamic degradation.
hawk37, I understand that the ATR series of aircraft have large performance restrictions when using any thickened fluid (type 2 or type 4); similarly the Saab 2000 has revised takeoff speeds and trim settings. And possibly the Dash 8 too. Some BAE turboprops have notes to crew re increased control forces.
--------------------
Unless specifically authorized everything else is forbidden.

[Knold]

I know it is but if it is like alatriste said right now deicing fluids approved by the AEA must comply with fluid´s flowoff characteristics test criteria then that would mean the fluid wouldn't be approved unless they had changed it since the early problems appeared. Correct or not?

[mutt]

Knold,

The assumed temperature is not a derate in itself, or so I was told by a performance engineer

According to Mr Boeing, there are two types of DERATE, fixed and assumed.

[edited to remove exclamation mark.... :):) ]

Mutt.

[alf5071h]

Knold, many things are hidden in words.
Manufacturers may ‘approve’ de-icing fluids, but often the small print indicates that their approval is limited to airframe materials i.e. the fluid will not harm the structure, seals, plastics, etc. Few if any manufacturers will give unequivocal aerodynamic approval for de/anti icing fluids; the fluids themselves are a contaminant, but supposedly with known characteristics.

When type 4 fluids were introduced several ‘brand’ names met the same ISO/SAE specification, but each had their own formulation. Some of the more exotic formulations caused problems, one at least was removed from the market, and others possibly re-branded as lesser types or ‘+’ versions. The ISO / SAE specification may not take account of differing glycol formulations used for environmental reasons; note fewer problems in the USA (fluid type or regulation / training?). Also things such as dynamic viscosity may not be considered, where a fluid will flow more readily with increasing airflow, but if the fluid falls into an aerodynamic quiet area (control gap) it thickens in the lower local airspeed and sticks in place. Then there are issues with thickening agents, colourants, dry out characteristics; although the latter was addressed with a specification revision.

I am not familiar with the AEA ‘approval’; what processes or to what specification do the AEA test the fluids. How many flight tests have they conducted?
A major problem for the industry is that there is no regulatory ownership of de/anti icing fluids. My understanding is that the ISO/SAE specifications are similar to industry agreed standards and guidance, and they do not regulate operational use. How can ISO/SAE govern the application or actual operating environment, have they conducted flight tests? If they have, in which aircraft and in what range of conditions, where is the supporting evidence?

I do not know of any public documents relating to the flight characteristics of fluids since the very old USA (FAA?) work based on a 737; this indicated a small, but ‘acceptable’ performance degradation with what I suspect was a type 2 fluid. Several manufacturers have in recent years conducted aircraft handling and aerodynamic tests with a range of fluids after a spate of in-service problems; I have not seen any published results. I believe that one manufacturer tested both aerodynamic and climb performance and although some performance degradation was noted, I do not know by how much or whether it warranted any change to their operating manuals.
I suspect that current problems are centred on the slower speed aircraft, turboprops, etc, and/or with manual controls; for which the type 3 fluid was designed, but has not seen wide service.

[Knold]

Alright mutt, I think that might have been his point which I obvoiusly missunderstood but thanks for pointing it out to me with an exclamation mark.

The reason for this whole thing is the JAR-OPS requirments for what shall be included in the performance chapter of an OM-B.


JAR-OPS1 Subpart P

4.2 Additional Performance Data. Additional
performance data where applicable including:

(a) All engine climb gradients;
(b) Drift-down data;
(c) Effect of de-icing/anti-icing fluids;
(d) Flight with landing gear down;
(e) For aeroplanes with 3 or more engines, one engine inoperative ferry flights; and




I know that it says "where applicable" but yeah, I would like to know.

Now we all have our feelings regarding JAR-OPS and its "benefits" but a rule is a rule is a rule....