Jason -
Howdy !
I enlisted w/ the 122nd Tactical Figher Wing of the Indiana Air National Guard in Apr 1972, 1 mo before HS graduation. Went right off to Basic, immediately thereafter.
Spent 1st 2 years as a " Traditional Guardsman " in the Aircraft Fuel Systems Shop, before hiring on full-time as a CIvil Service " technician " in the newly-formed " Environmental Systems " shop. We had F100D / F's at the time, and still had 7 F-84F's that we were dispersing to various local parks, after they were retired from service. My first on-aircraft job I was assigned after return from my 10wk Tech School @ Chanute AFB, was to strip incidental parts off of one of the F-84, before it was towed away. There was a T-33 sperated in 2 pieces in the hangar, and was being crated up for shipment out.
The 122nd converted over to F-4C's in 1978, and I was caught up in a modification to remove the trailing edge " BLC " ( boundary layer control ). The base @ Ft. Wayne, IN was located in postition & latitude that the ponds, lakes, rivers; and vegitation made it extremely humid..... especially in the summer time.
As the Environmental Shop Chief, I became embroiled in a large problem on the F-4 ECS. I found that when pilots selected cooler temps on the cockpit temp control knob, cabin pressure @ altitudes of around 10,000ft AGL and less.... would " surge " + / - 2,000 in cabin altitude; as shown on the cockpit gage.
This of course gave pilot's' a very unpleasant " WAH - WAH " effect on their ears, due to the felt pressure flux.
F-4s had a cockpit Environmental Control System outfitted w/ a water seperator, which was introduced to the ECS via an extensive system MOD done on all F-4s.... as a result of the Vietnam experience. What initial
SE Asia F-4 opertations showed was that when pilots selected cooler cockpits temps in those hot/humid conditions, thier fwd vision would be obstructed by dense fog eminating from the defog ducts located @ the base of the windscreen side panels. This was a major hazard to safe flight ops, and a mod to add a water seperator to the ECS was hustled through the aircraft modification process in near record tiem,even though testing showed the new ECS Mod had significant shortcomings.....
The cockpit ECS mod introduced a water seperator, anti-ice controller, anti-ice valve, misc lines and a lag chamber. The anti-ice valve had 2 ducts quipped with 2 bellows segments on the in-going engine' bleed air duct and outgoing de-icing ducts for water seperator anti-icing. When the water seperator' coalescer bag started to ice up... sensing lines sensed the pressure drop across the seperator; and the anti-ice controller would send a pressure signal to the anti- ice valve. The valve would then modulate open/closed to de-ice the water seperator. [ if the coalescer bag were to ice up and the H2O seperator become clogged w/ ice.... airflow woudl cease to the cockpit. The hot bleed air tap-off point and pressure sensing ports for the anti-ice ducting circuit were located AFTER the ECS pack's " Bleed Air Pressure Regulator ". When the anti-ice valve operated, the BAPR sensed a drop in the ECS pack pressure, and opened to let in more bleed air to compensate. This additional bleed air was introduced while the wter seperator anti-ice valve was open, hence.... the " WAH- WAH effect on the aircrew's ears.
The anti-ice lines would be forceably flexed outward @ the bellows during the ECS pack's pressure flux. After enough cycles of this flexing, the bellows would rupture; and razor sharp thin metal shards would FOD the entire ECS bay. To access the bay, one was required to remove 118 apex screws... using a #2 apex bit and holder... and a " speed handle ". The belows failures of course resulted in the aircraft aborting, and doing an RTB as an emergency; and thereafter grounded for repairs. When the 118 scew access panel was removed, it was common to see rounded grooves in the bottom inside structural rib on the door, when the bellows segments were forced outward so far that they rubbed on the rib, Normal clearance would have been around 3/8".
The FOD finding and removal was complicated by the fact that the ACS Heat exchanger sat atop a fixed fin exhaust casting, that was basically installed as the first itme on the aircraft's center line " Keel ". It was located in the bottom of a deep constantly narrowing downward chasm along the kell, so of course.... this is where the FOD migrated to.... and it all had to be found... and removed. The large/ sharp edged heat exchanger that first had to be removed, was attached to the center line keel behind it.. by an un-lubricated steel bolt... passing through an unlubricated steel bushing, bolted to analuminum tab on the keel.
Theres' 5 things F-4 Environmental Systems were absolutely forbidden to do...... and, the first 4 were....
" break that aluminum tab " . At the same time, the excessively heat cycled, rusted together bolt / bushing assy resisted attempts @ its removal. Beyond all that.... we ALL of the other ECS components andlines first had to be removed from the ECS bay, before the heat exchange could even be accessed.
We had 28 F-4s..... and Summer was a nominal 3mo long. The one year I kept records.... our shop worked 96 various Environmental systems gripes....a combination of ECS squawks and cabin pressure writeups.
But of course.... the cockpit pressure surging " CODE 4 " grounding write ups dominated our workload.
We flew F-4C's for 8yr, and then up-gunned to the -E model in 1986. It had the same cockpit ECS system.
We then flew the F-4E's until latter 1991, when the unit converted to F-16s right after they returned from the " Gulf War ". So.... 13yr of fighting that particular problem.
Why do I tell you all this ? I called out to the Aircraft Systems manager @ OGDEN Air Logistic Center, and the ECS Component's Manager @ Oklahoma City ALC, because by design and configuration.... there was NO way the cabin pressure surge problem could ever be fixed in the field. What HAD TO take place for an enduring " FIX "... was a modfication of the ECS water seperator de-ice system to one that did not cause the cabin pressure surging. IF the plane flew high enough above the humidity.... there was no surging. If flown in a dry/drier climate w/ low humidity... there was no surging.
Our record for the number or F-4s grounded in one day @ our base in Ft. Wayne was 4. Add to that 3 F-4s in Phase Maintenance and 2 out @ the Depot for " speed line " repair work + other F-4s grounded for various other reasons ( principally avionics ); and one see's the need to NOT have any more F-4s grounded than was avoidable. 4 grounded for surging in one day was a hit against our fleet's availability that was just to ridiculous to be allowed to conitinue ( and I felt that way in the Summer of 1978 ).
I became the voice of one crying in the wilderness, and was forced to reach out to every other F-4 Environemental Systems Shop on the Air Force, Air Force Reserve; and Air National Guard. At the time I identified the problem to the ALC System's Managers; the total F-4 fleet for the above users was 1,420.
SOME of these flew in humid climates... some did not. The problem was not important to all F-4 units, but
WAS a real _ _ _c h for those locations that had the humidity. I found 2 other ANG outfits that also had the surging problem on their F-4s. I authored and submitted discrepacny report on the F-4 ECS problem in 1978, and it was put under study by the " Systems Manager " @ the Ogden Air Logistics Center....
I had to submit a " Fraud , Waste; and Abuse " report to the Air Force IG, to get the AF to force Ogden ALC (aircraft side ) and Oklahoma City ALC ( systems components side ) reps to comeout and verify the problem existed as Ihad reported.. They finally came to our base (during a cold snap ) in Jan 1979, and we were still able to show the " engineers " and Systems Managers the surging phenominon during ground engine runs.
The cabin pressure surging problem was given a formal project investigation number, and I was ultimately able to force the ALCS to make prioritze the problem as one of the top 10 problems on the F-4, that were negatively impacting aircraft availability. THAT allowed them to obligate $$$ for a systems MOD.
To minimize FOD damage to F-4's and to avoid in-flight emergencies and aircraft grounding; I was able ( during a conference out @ Ogden ALC ) to get the Systems Manager to authorize requesting units the permission to " de-activate " the water seperator & its associated anti-ice system. Aircraft mods were introduced by what were called " Time Compliance Technical Orders " ( TCTO's ), and the de-activation was assigned TCO number -908. We de-activated the system on every F-4 we were assigned over the 13yr period.
13 yr after I reported the problem, they had finally engineered a mod that used an electric modulating valve for anit-icing, and it was going to take time to field as a TCTO.... and cost a lot fo $$$.
I submitted " de-activation " as a suggestion through the formal AF Suggestion Program channels, which offered cash awards to suggestor's if their idea was approved; with award amount based on how many $$$ the suggestion saved the Air Force... not to mention how much aircraft availability would be enhanced.
My suggestion simply removed the coalescer screen assy & bag, and capped the two anti-ice valve sensing lines. Since my idea ( to the engineers ) was NIH ( ' not invented here " ), I was viewed as being well outside any possibility of having my suggestion ever being seriously considered by them for final adoption.
Through over site by the AF's Inspector General's office, I was able to force OK City ALC to allow me to run my suggested -908 mod on their indoor-mounted F-4 ECS system, for in-lab instrumented test and analysis.
The incoming super hot " bleed air " was ducted out the bottom ot the heat exchanger mounted in a fixture. so the test lab got very hot as the ECS was run indoors. The Engineer's suggested electric anti-ice valve system would not allow cockpit air from the pack's cooling turbine to ever go below 36*F . Since the simplified ECS mock up system let the cooling turbine exhaust to ambient... it had potential to cool the test compartment.... some. As the engineer's system ran, the room continued to get hotter & hotter.
I was the allowed to set-up the test ECS per my desired -908 configuration, which took minimal time and effort. With the cooling turbine again exhausting to ambient in the test room.... I was able to cool the entire room down to 42*F... despite the input of hot bleed air being made by the heat exchange exhaust. My mod cost $ .98 for 2 stainless steel caps, a few minutes needed to de-panel an affected aircraft; and around 20 minutes to gut the EC water seperator, and install the anti-ice valve pressure sensing lines. Easy.
During the 13 yr episode.... the number of F-4s being flown by Air Force components was steadily on the decrease. Therefore, the need for the ECS mod began to become less & less important. But, the engineers had a mod they invented, and they already had the money for fielding their mod ready @ hand.
In the end. I was awarded $500 for my suggestion..... to " throw me a bone ". The engineers put their mod on the F-4's remaining in service, albiet ...a lot smaller number of aircraft than were in service back in 1978... when I exposed the whole F-4 ECS debacle.
As it turned out, the 122nd's had most of its F-4E fleet's ECS modified in 1991, when the Gulf War started.
The engineers took 13 yr and oodles of money to maintain a water seperator on the F-4 cabin ECS, just in time for some of the F-4E's, -G " Wild Weasel "; and RF-4C's to be sent to the harshest, driest desert conditions on the planet !
Karma's a funny thing. I had already transfered over to the F-4 Electric shop, when Maintenance Control called in the summer of 1991. Both Environmental Systems Technicians were not present for whatever reason, and THE last F-4 the unit was scheduled to fly out ( converting to F-16c ) had a cabin pressure surging writeup, and was grounded. Since they knew I knew how to fix the problem, they assigned me the duty. Despite having a kit for the new Engineer-develpoed mod available for install, senior management was keen to see that last F-4 depart on time ( we were THE last AF / AF Reserve / Air Nationa Guard unit to fly the F-4, before they headed off to be modified to become drones / arial targets. ). President Reagan was going to on the air, to announce the United States transfer of F-4's to Greece, and it was the planes leaving 122FW service that he would be eluding to. WIth all that as a back ground to the excitement, I told everyone in my chain of command and Maintenance Control... that I could have the plane fixed in 45min.
So..... the last F-4 to leave service and leave Ft. Wayne was one with the water seperator anti-ice system
de-activated.
Well... that's how I remember it, anyway.
You asked.
With regards,
357Mag
