With Double Flame-outs, The Stress is Additive
When a Pinnacle Airlines regional jet flamed out both engines in October 2004, it was ultimately revealed that the pilots had exceeded the performance envelope and simply demanded too much from their engines at too high an altitude and too low an airspeed.
Unfortunately, their dead engines also had a known (but not to them) characteristic of not readily rotating, due to a high breakout friction attributable to very close-fitting blade tip tolerances in the CF34. Consequently, they couldn’t achieve RPM for a relight nor light off from an APU-supplied starter motor start. The story of the A330 Azores Glider is too well known to relate here–and there was also the Sept. 30, 2005 University of North Dakota Citation II emergency crash-landing near Beaver, Alaska, after both engines flamed out at 9,200 feet in cloud. The Citation’s engines quit following a "loud bang" several minutes after the de-ice boots were cycled to shed accumulated ice.
All complex crises and enough to put icicles in the veins of the coolest airframe driver, you say? Well, we’re familiar with one that’s achieved little publicity, but might equal or beat them for persistent stress value for pax and pilots, rain, hail or shine.
A couple of months earlier than Pinnacle in July 2004, a Beechjet 400A reg: N455CW with nine persons on board flamed both engines out while descending from flight level (FL) 410 to FL 330 over the Gulf of Mexico about 100 miles west of Sarasota, Florida. Passing FL 390, they felt a jolt and heard a bang. About 30 seconds later, the pilots realized the airplane was losing cabin pressure, declared an emergency and accomplished the emergency descent checklist. The pilots stated that at about FL 350 they’d noticed that every cockpit warning light was illuminated and that both JT15D’s were not operating.
Understandably, they’d assumed depressurization and not noticed the flameouts because at idle there’s not a lot of engine noise and the descent attitude was maintaining the desired airspeed. After several attempts, they were able to get the No. 2 engine restarted at about 14,000 feet and diverted to Sarasota because they were relatively close. The final report for ENG04IA021 isn’t out yet. The following year, on Nov. 28, 2005 another Beechjet (N691TA) lost both at FL 380. They were in clear air when they also heard two loud "pops" and saw their engines wind down. They glided an ILS into Jacksonville without being able to get a relight (NTSB’s DCA06IA007). Both incident jets were from the Cleveland-based fractional provider Flight Options.
The common denominator proved to be fuel. In both cases fuel was lacking but it was also plentiful, i.e. only lacking "a little something". Until these developments, the only fuel-related Beechjet event had been the notoriety of having had a fuel-tank explosion during ground ops. The NTSB said in January 2005 that N455CW had a much lower than normal amount of anti-icing additive in its tanks. Unlike some similar corporate jets, Beechjet 400As are not equipped with fuel heaters, so the additive is critical for allaying ice formation in the fuel. The fuel sample from 455CW had only 0.023 PPM of Prist content. The recommended ratio is .10 to .15 PPM.
What is Prist? It’s a fuel system icing inhibitor (FSII) or Diethylene Glycol Monomethyl Ether. FSII is often referred to by the generic trademark Pristr. It makes fuel more expensive by about $.03 per gallon. The active ingredient DGME can also damage filters, tank sealants and bladder tanks in higher concentrations over a lengthy period, so owners are loath to overdose with it, particularly as it separates out over time. Think of fuel icing as the internal icing hazard; one that can strike even in clear blue skies. When a plane climbs, the temperature drops and the fuel cannot hold water in suspension. This water can separate out and freeze in fuel lines blocking the flow of fuel. Prist is also an anti-microbial agent that helps to keep sludge from forming in the fuel systems. This property is important if the airplane flies infrequently.
The Bite of the Additive Adder
At FBO’s the Prist is supposedly added into the fuel at the truck, but as one Beechjet pilot anguished: "After I found out what happened to 455CW last year, I now carefully check the truck that is supposed to be injecting Prist during refuel and at least a dozen times in the last year either:
- the Prist tank was empty
- or the injector was not turned on
But even if the Prist is premixed, what solid evidence is there that a pilot is getting the right mix?" The answer is none.
He went on: "Last month the tanker truck shows up and about 10 minutes later it pulls away. I said to the line super, "That went pretty fast." His reply: "That load did not have Prist in it when we checked. I refused the shipment." So if my line guys had not been on the ball we would have filled up with straight Jet A."
The Beechjet 400A also serves as the basis for the military T-1 Jayhawk tanker and transport aircrew trainer; 180 were delivered between 1992 and 1997. The military T-1 also has no fuel heater and so the military pilot will always be descending when he drops to his fuel temp limit of -40C. In over 11 years and about 250K hrs, the T-1 is without a mishap of any sort, let alone dual flame-outs. Perhaps this is because the military fuel additive is premixed.
Not so Pristine a Process
At an FBO it’s a different story. One FBO "linie" cautioned thusly: "The Prist bottle can be full, and the injector turned on, but you still may not be getting Prist…it is possible that the Prist pump has burned out, because the line guys went a week without checking the bottle. If you run the pump too much without running Prist through it, it can burn out. At least this is what the GSE guy at a major east coast FBO told me. In any event, here’s a word to the wise. There’s a little glass jar container about three inches in diameter and three inches high next to the injector switch. There is a very small pipe that runs halfway up the jar from the bottom up. When the injector is on, and fuel is pumping, you should see an inch or two of Prist on the bottom of the jar, and a little dribble of Prist coming out of the tiny pipe. If the Prist pump isn’t working, you will NOT see the dribble coming up from the small bore pipe. In your own interests, watch that like a hawk."
One FBO Manager said: "I have encountered aircraft that require Prist, yet the pilots refuse it because they don’t want to pay for it. We have a regular customer who makes a habit out of this. As such, the importance of Prist may be lost upon the less educated/experienced line guys. It’s just something to think about the next time you pilots are shocked and horrified that a line guy didn’t put Prist in. I find the Prist related QC issues frustrating. My employer is a ‘preferred’ FBO for two of the three largest fractional operators in the country. In order to achieve this distinction, we have to comply with both companies’ rules and SOP, as well as get audited by reps from each company."
He suspects that his operation is being audited by his own company reps, as well as reps from its fuel supplier. "The QC records we use are provided by our fuel supplier," he said. "Where I’m going with all of this is that nowhere have I seen any requirement, nor any place to log any tests, of Prist dispensing. The documentation I am familiar with includes daily, monthly, and quarterly required tests. In other words, I don’t think anybody is checking up on us to make sure that our Prist dispensers work properly. We now know what happens when they don’t."
Water’s not drainable
He’d spoken with an unnamed source close to the investigations. "Fuel samples allegedly came back shy on Prist, but there was also a high water content suspended in the fuel," he said. "Sumping the fuel tanks would do no good since the water was suspended. So you do need that Prist and in the right proportion. We only use trucks with a visible injector, and you can hear that ‘clicking’. You can see the Prist Selector in the ON position, and the 1.5" clear cylinder periodically shooting fluid into the line (the clicking sound). Helpful and reassuring but now all we have to worry about is, ‘what’ is in that cylinder–is it really Prist–and how much is going in? You can have all THREE things and never be certain that there is the appropriate amount of Prist being injected. When they pull a fuel sample from a downed airplane, all that they can see is that there was not a sufficient quantity of Prist injected. Ultimately, that will come back and bite the FBO in the ass. I don’t see how the legal tango can be avoided."
The Thaw Point
So what is so frightening about these flameouts? Assuming that the engines flamed out because of ice formation in the fuel, the airplane will be descending faster than the ice will be melting. So in a really bad cold soak situation, the ice build up is so significant that there is nowhere near enough time to "get the melt" while you’re on the fast glide (fast is required for those relight RPMs). There won’t be any relights and if you’re a corporate passenger, you’d better hope that your pilot has been practicing his deadstick approaches.
The word has filtered out: some FBOs have started to advertise "premixed Prist". Sounds reasonable, but are you wholly convinced? Prist that’s been mixed in for too long can separate and drop to storage tank bottom.
How will the VLJs Fare?
So tell me, if you’re a corporate jet user endowed with the power of decision, will you ask whether your ride has a fuel heater? One final word: We’ve heard from different sources that there were at least two other Beechjet double flameouts (U.K. and Danish possibly), but we’ve no details on them beyond what’s in the six incidents recorded at http://www.iasa.com.au/beechjet.htm. What we do have some details on is the fifth.
On June 14, 2006, the aircraft took off from KBWI (Washington-Baltimore) and was headed to Florida but declared an emergency and diverted to KORF (Norfolk Intl Va). There’s no mention of the incident in the FAA or NTSB accident/incident databases. Maybe there’s a case here for FAA review of the whole indispensable subject and even the certification basis of having no fuel heaters – such as in the new range of VLJs. Do you think $0.03 more per gal is too high? Think again. The price of no Prist could incur a much higher cost.
Controlling Fuel System Icing
Prist additive has limited solubility in jet fuel, but is completely soluble in water. When dissolved water separates from the fuel, some amount of Prist additive quickly leaves the fuel and preferentially dissolves in the water. This depresses the water’s freezing point. As the fuel gets colder, and more water particles appear, more Prist additive leaves the fuel and enters the water, and the aircraft’s fuel lines stay clear.
Why you should use a fuel additive
All turbine aircraft fuels contain some dissolved water. It cannot be extracted because it does not exist as particulate water. When an aircraft rises to flight altitude, the fuel cools and its capacity to retain dissolved water is reduced. Some of the dissolved water separates out as discrete water that can form into ice crystals or remain as a supercooled liquid. When supercooled water strikes a tubing bend or a filter, it can freeze quickly and block a fuel line or filter. If suspended ice crystals are present, they can also block a filter. The Prist anti-icing fuel additive controls icing in aircraft fuel by depressing the freezing point of water.