Internal Engine Icing - Beechjet 400


One might say, what? Engines are too hot for internal icing. This article threw me for a loop. Please forgive me as I lost the URL for this article but I retained the part of the article which I found very interesting. The main topic of the article was safety for business jets. Ya think this is perhaps a problem with other twins and not just the Beechjet 400? And does anyone have any updates on this?

"The NTSB has also recently called for urgent action from the FAA over a series of high-altitude, dual-engine flameouts involving Beechcraft Beechjet 400 business jets. The latest incident took place in July, when a Beechjet 400 operated by fractional provider Flight Options suddenly lost power while descending from 41,000ft to 33,000ft in IMC. The pilots were able to restart one of the Pratt & Whitney Canada JT15D-5s and land safely. In another incident, in November, another Beechjet 400 had to make a deadstick landing after dual engine failure during a descent from 38,000ft.

The safety board points to P&Ws own investigation into the flameouts, which revealed that with engine anti-icing turned off it was possible for ice to build up on the leading edges of the low-pressure compressor stator, leading to compressor surge and/or flameout. The suggestion is that ice crystals melt as they enter the engine then re-freeze on the stator blades. The NTSB wants the FAA to work with engine and aircraft manufacturers to actively pursue research to develop an ice detector that would alert pilots to internal engine icing."


The problem is a Beech Jet problem. There is no fuel oil heat exchanger. A fuel/oil heat exchanger uses hot engine oil to heat cold fuel, and the cold fuel to cool the engine oil. It’s not a big deal that it doesn’t have one, so long as Prist is used in the fuel. Prist is an anti-microbial/anti-icing agent for fuel. If Prist isn’t added or isn’t mixed at the correct ratio, the water in jet fuel (common) can freeze and plug up the fuel filter. Plugged fuel filter can lead to a flame out. As the aircraft descends into warmer temps the ice melts and the filter becomes unclogged and we can start the engines.

The fact that this has happened 2 different times is scary though.

There is no way for a pilot to know that Prist has been added or not. Most FBO fuel farms have Prist premixed. If it isn’t at the right ratio or is missing no one knows. Some FBO’s will add it as requested, in which case they can attach a can of Prist to the fuel nozzle as it’s pumped into the a/c, or add it to the fuel as the aircraft is refueled via single point. But again does the pilot have any idea if the ratios are right or not?

On a personal note, I used to work line in Western New York, PRIOR to my flying days (HINT). We had a truck where we could add Prist as requested. It wasn’t checked at the start of my shift and the next day we caught that the Prist was empty. No telling how many a/c we fueled that requested and needed Prist that didn’t get it.


Don’t know if you are claiming there is some other cause of these flame outs, but the quotes from above would indicate a problem totally unrelated to fuel icing.


Just read the whole post :blush: I hadn’t heard about the stator vain icing. We’ve done alot of talking here at FSI about these 2 incidents, and I’ve always heard the samething; Prist and heat exchangers. I’m not sure where the stator vain statement comes from. It would be possible for water to freeze in the stator vain seeing as they are quite aways form the hot section of the engine but it seems like an unlikly cause.


Had another thought. This a/c is also known as a Diamond Jet or a Mu300. It’s been around for years. The current production is a Hawker 400XP with JT15D-5 engines on it. The previous runs were as a Beech Jet and a Mu300 both with JT15D-4 engines. Maybe something changed in the engine, but I can’t find any accident report of a Mu-300 b/c of engine flame out.

So the long and short of it is, I have no idea.


USAF operates 179 of the T-1A Jayhawk.


Found the URL. My quotes are from near the bottom under “LearJet Accidents.”


Was wondering about this because I can’t find anyone who knows the scoop and was wondering just how many jets have these types of engines and might be at risk.


Alot of aircraft have these engines. Most Cessna 550/560’s (Citation II / V, Ultra) from 80’s and 90’s. The Cessna and Raytheon fleet number in the thousands of aircraft (~5,000), times two engines each.


Your are 100% correct. And in all my days flying Ultras and II’s I’ve never had an engine even hicup (sp?). Neither has NJA, which has been operating II’s and Ultra’s from the time they were new aircraft.

So I don’t know what the issue is. Maybe the Beech Jet has a different shape to the engine inlet? Maybe it was just one of those fluke things, that happened twice! edit 3 times!!

Thanks for the USAF point out. Have they had any accidents/insidence of this type?

Found some NTSB reports for Beech 400’s:

NTSB report with a/c about to enter IMC, not clear if a/c was still in VMC, but either way ice doesn’t build up that fast.
NTSB report with a/c in VMC conditions.
NTSB report with a/c in IMC


There have been 4 reported dual flameouts in the BeechJet. 3 of the crews got an engine started, and the one crew deadsticked it into JAX. All of the incidents involved a power reduction for a descent, operations in the high 30’s, and with visible moisture in the vicinity. Kinda odd huh ? And just for fodder, here’s my personal experience with this type of incident. I flew a 2001 BeechJet 400A for just over 3 years and about 2000 hours. We had an 8pm departure from Dulles going to Las Vegas . Nice night, a few cloud tops around us, and us just skimming a few of them. We were cruising along at FL380 or390 and were given a descent to FL240, starting down for a fuel stop in Wichita. It was late and we were both looking out our side windows, when something just didn’t feel right. A vibration change, change of sound, whatever it was. I quickly scanned the engine guages only to see the #2 engine spooling down through 30% N1. Remember, they idle at 52%. Not good! I alerted my partner, turned on the autoignitions, and it stopped at 26% before accelerating back to normal. Talk about waking you up! We landed at ICT without incident, had the mechanics at Raytheon FBO look at it and discuss it with out maintainance coordinator. The verdict? “Everything looks ok. You guys go fly it.” Hmmmmm, 11pm, 2 hours to go, and engines that are doing weird things? Not a warm and fuzzy feeling. But soldier on we did, and never experienced anything like it again over the next year or so. Talked to a P&W senior engineer, and she told me that in testing, they had seen enough ice form on the stators of turbofan engines idling ON THE GROUND to almost totally block airflow to the engines. I know inlet icing sounds quite strange, and perhaps it is a problem with fuel controllers, or fuel icing, all I know is I’m happy to not be driving a BeechJet anymore!


Raytheon has issued new procedures for BeechJet and 400XP operations in icing conditions. They include a requirement for engine ice protection to be on during operations in the vicinity of visible moisture, and a removal of the limitation to reduce power below 90% before turning on engine anti-ice. Here are 2 links, the 1st from AIN magazine with a brief explaination of the revision, and the 2nd is the NTSB letter to the FAA administrator with their recommendations. The NTSB document goes in depth on the weather conditions and stator vane icing.


Now that clears things up in my mind. A blockage of flow. I was thinking that the ice released into the engine, flaming it out.

Any ideas why we never heard of this on MU300’s? at least not that I’ve seen/heard

a side not that in the CE560XL there is now a requirement to turn on the ignitors if the power is going to be below 70%. Related??? I don’t know.


Perhaps they need to add a wobbly, coat hangar inspired, carb heat switch. :stuck_out_tongue:

Mitsubishi switched to the -5 engine just before selling the program to Beech. Beech then made a number of improvements before releasing the Beechjet.

The August 2004 and December 2005 FLYING magazines have nice reviews of the Hawker 400XP. J. Mac seems to like it more than the Citations.


In my experience I have never heard anyone like the beechjet, either from a maintenance point of view or passengers. They also seem much louder than other aircraft equipped with the same engines. Just my 2 cents.


Chesers, you couldn’t be more wrong! Well, sort of. Passengers LOVE the cabin on the BeechJet, as long as there aren’t more than 4 of them. The cross section and typical seating arrangement (center club), make it very roomy when there are only 4 pax and the seats are tracked all the way back. Also, It is a very quiet airplane inside, as well as having the best ride of anything in it’s class. I spent 3 years flying a 400A all over the country, especially up and down the east coast, and when the airliners were reporting moderate turbulence, we didn’t even get a ripple. And yes, we were at the same altitude and position as the airliner reports! As for maintainance, the airframe is very robust, with very few problems. The avionics, on the other hand, can be a nightmare. EVERYTHING electronic on the airplane flows through a series of I/O cards in the nose compartment, with totally unrelated items on the same cards. I have turned on the coffee pot and had the #1 Comm transmit!!! It flys like a truck, has crappy range (1000 nm) when flown at max cruise of .78Mmo( but if you wanted to go slower, you would’ve bought a Citation), doesn’t want to climb above FL390, and only has a useful load of about 700 l lbs with full fuel, but it’s a very comfy ride. Oh, and they are noisy SOB’s from the outside!


It should be noted, that the icing that the P&W engineer is on the first stage compressor, the one visible in the inlet, and not at some point in the engine where there is heat from compression or combustion.