BAe 125 Series 800
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Confusion
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Aircraft; Manuals
I am writing over some concern and confusion over the TKS Fluid De-icing System that I experienced on a HS-125 aircraft [in] May 2014. I have filed reports in the past over this system and have another issue in regards to this. The situation occurred a day prior in May 2014 when I airlined to pick up the HS-125 at an FBO. The airplane had been worked on by Hawker-Beech and had a test flight done and was released. When I picked up this airplane; I went through my normal preflight checks. Numerous leading edges had been removed and hence the need for the test flight; so I wanted to test the TKS panels to make sure they worked. It took quite a bit of priming but after five separate; two minute primes; I had good flow everywhere except on the Outer Panel # 7 for both the left and right wing. On this panel; TKS fluid was flowing out very well except in the middle one-third (1/3); maybe about 8'-10' inches in length. In this middle spot there appeared to be no fluid running out at all. Everywhere else on this panel and others; fluid was coming out strongly that it would fall off the wing and puddle up on the ground. So I therefore wrote this as well as another issue up. So the next day I come out and see that the corrective action [in Logbook] was to operate system and confirm system functions properly. This came across to me as nothing was done except to run the system and it was confirmed to be working. So; being surprised to see this I ran the TKS System. As what I had witnessed the day before; it was exactly the same. On every panel TKS flowed strongly out of all the panels except on the middle 1/3 of the Outer Panel # 7; for both the left and right wing. Seeing this I searched out a Hawker Beech Mechanic to question him on this. I went into the Hawker Beech Hangar to find a Mechanic. I was told by the Mechanic there that our Air Carrier's aircraft were actually worked on by a different set of mechanics from another hangar. This Mechanic said he would call for one to come to our plane. Therefore I returned to the plane to continue with our duties while I waited. Eventually a Mechanic showed up; but he wasn't wearing a Mechanic's uniform so he might have been a Supervisor or such. I then proceeded to explain my situation about the TKS panels and we ran the system and went out to the wing to look at the panels. I then showed him how; on both Outer wing panels; that the middle 1/3 had no fluid. He then proceeded to run his finger across that portion of the panel; and by doing this you could make out the faintest amount of fluid on the panel as it smeared. However it was nowhere enough to cause dripping and really even enough to wet the panel; but sure enough if you ran your finger across you could feel a slight amount of TKS fluid on your finger and see a slight discoloration of the panel caused by the fluid. He then proceeded to tell me that the Maintenance Manual (M/M) does not stipulate how much of a fluid rate a panel is to have. In their mind any fluid whatsoever; no matter how little the amount is; from a maintenance standpoint; the panel is acceptable. So; in this case; even though every other panel and even on the panel in question; but on the other areas was flowing so much fluid that the fluid falls to the ground and puddles up; that in this section because there is enough fluid to make your finger feel wet and cause come discoloration on the panel but no real fluid flowing out; it was acceptable. I admit I was surprised to hear this and just the mere fact that I have been in other airplanes where the fluid flows out strongly along the whole outer panel that I was surprised how this would be acceptable. The Mechanic also stated that he felt in-flight it would work better and also you would get some span wise flow along the panel to make up for this lack of strong flow in the middle of the outer panel. The thing that is unique about the Outer panel on both wings is that it is a different type of panel than all the other panels. The other panels have what looks like a mesh attached across the leading edge of the panel. Whereas the outer panel on both wings is a solid leading edge but has minuscule holes drilled into it. I have never been told why these outer wing panels are different but I always assumed it was because of them having the ailerons aft of them. The other panels with the mesh give the appearance of fluid flowing throughout the mesh before separating out into the airstream. These outer wing panels appear to just flow fluid out and immediately hitting the airstream causes the fluid to flow aft. I bring this up as in what I found when checking the system after a flight. However; seeing how the sign-off was done on the Maintenance write-up and by going from what the Mechanic said; we flew to our next destination. Unfortunately; due to the high temps and short flight; I didn't get a chance to run the TKS System on the first leg other than the normal priming we do. However; on our second leg we flew into ZZZ1 and I ran it for the last 12 minutes of flight; timing it to shut-off as we turned off the runway from landing. I like to do this whenever I am suspect of the TKS System. I mentioned this technique in a previous report so I won't go into the details why; but I have found that when you post flight after landing; you can see all the TKS fluid on the wing and tail and how it flows aft. It really gives you a good picture of how the TKS fluid is flowing on the leading edge of the panels and aft. So after landing; I went about looking at how the TKS had flowed out on the wing and tail panels. Sure enough as I had expected; there was good flowage on all the panels and aft of the panels covering the wing and tail in every section of the panels except in the places in the outer wing panels that I had discovered the other day but was signed-off as acceptable. However; if I ran the system again on the ground; I could still get a miniscule flow out of the middle 1/3 of the outer wing panels. The amount was no more than enough to wet your finger but was nowhere near enough that you could visually see it coming out and falling off the wing to the ground like the other sections on the panel and every other panel. However; by going by what the Mechanic said and did; this was acceptable because no minimum flow was listed and as long as I can feel some coming out; I am good. However; just looking at the wing itself; it sure doesn't give the appearance of offering adequate protection as there was no aft flowage of the TKS fluid. So after describing this whole situation; I am asking is what the Mechanic said correct? Is there truly no flow amount required of a panel? And if so; even the faintest amount coming out that requires you to rub your hand across the panel so you can feel it; even though it is not visible; is acceptable? Also; why I am asking questions I am curious why the outer TKS panel on the wing is different from all the others. Unfortunately; I have yet to fly in icing conditions with this airplane so I am not able to verify if the panels in question would prevent ice buildup in the areas suspect. So I am filing this report in the hopes I can get answers on these questions.
Reporter stated he was told the outer TKS panel on the left and right wing leading edges has two deicing fluid lines going to them; but only one line for the other panels. The Hawker Beech HS-125 carries a 10-gallon tank of TKS fluid that has an expected 108 minutes of use. If the rotary Ice Detector on the side of the fuselage sets the detector light on; they usually punch out of the icing condition in a few minutes; max maybe twenty minutes. The leading edge is all fixed wing; no movable slats or flaps. Other than what the Mechanic told him earlier; no current information about his questions have been answered yet.
A Captain questions if the miniscule amount of TKS deicing fluid weeping from the middle one-third of the outer left and right wing panels; compared to the other leading edge deicing panels; is sufficient to give adequate icing protection on the Hawker Beech HS-125 aircraft.