A twin tail tale
By: Tom Wondrock
One of my favorite engine programs was the TF30 Navy engines for the F14 Twin Tail Tomcat.
I had an amazing career.. right place, right time, and most importantly the right people. I thank you all.
Recently a friend commented to me about which aircraft I was referring to. I realized that there are those that may read this story and not remember the Grumman F14 Tomcat. I've included a picture to assist. To further help, it's the real star of the first Top Gun movie, not Tom Cruise and the hero of the Top Gun Maverick movie. When you look at the Grumman pictures of the emblem the Tomcat always has two tails. Grumman built great aircraft. Their solid designs carried naval aviators to many victories that made significant contributions to defend not only U.S. troops but defenders of many nations during the second World War. Following those traditions the F14 was an amazing airplane. Way better than it was portrayed by its detractors. (By the way, the threat imposed by U.S. fighters/ bombers to enemies of true Americans can be seen directly by how the communists in our congress limit the production of formidable deterrents.
As a bit of historical aside, the F14 had originally been scheduled for a higher thrust version of the Pratt&Whitney F100 engine designated the F401. It was a 28000 lb thrust class designation where the F100 initially for the F15 was a 25000 lb. thrust class designation. Testing on the F401 at the Pratt&Whitney Florida Research and Development Center (FRDC) in the swamplands of West Palm Beach Florida was not proceeding well. The increase in power required was proving a bit tricky and one of the main issues was the second stage turbine disk. The engine kept shedding this disk. There were stories of these disks being thrown across the test area and into the parking lot. One story was about how a guard at the post to enter the secured area once instinctively put out his foot to stop a glowing hot, liberated 2nd disk as it sped past him. Lucky for him he missed.
Not that the original F100 program was without it's faults, but maybe a subject for another time.
The U.S. Navy grew impatient that the F401 had not yet passed its PFRT (Pre Flight Rating Test) which would allow the engine to proceed to flight test.
The aircraft was proceeding at a better pace and Pratt&Whitney was placed in a bad situation. Sort of luckily, Pratt&Whitney was working with the USAF on another project, a swing wing bomber concept the F111. More stories here for another time. Pratt&Whitney offered to adapt one of the USAF engines to fit into the F14 until such time the F401 was ready for flight test.
These engines were the famous, or maybe infamous TF30's. The TF30 family were the world's first Afterburning Turbofan jet engines incorporated into fighter/bombers. Without a little research, I'm not positive which TF30 engine was the origin of the F14 engine though initially the TF30 was built in several models, the TF30-P-3, -7 and -9 and eventually the P111 in USAF F111's, though the internal design favored that the F14 TF30 came from the P3,7 or 9 family because the P111 family had an entirely different turbine design.
The TF30 also served admirably with the RAAF (Australia) and strangely Iran. Where they once again show up to save the day in Top Gun Maverick.
At one time Yugoslavia was in line to acquire some, but that never transpired. Maybe someday I can coax that story from the only person I know that may remember.
And there was also a non afterburning version the TF30-P-408 that flew in the USN Corsair.
I do ramble here but lots of history rattling around in this head.
So back to the original story.
About midway in the TF30's life in the F14, after an engine model upgrade from the P412A to the P414A I was tasked along with my senior engineer to make some "environmental " changes. Working with the design engineers we came up with some ideas and went about the decision process to pick the best candidate. From there we turned the designers loose and as they drew up the designs for the hardware changes Rich and I worked on the test plan to verify we could do what the customer requested.
Here's the story related to us, and maybe embellished a tiny bit by my imagination, but probably pretty accurate.
From this point, please try to visualize these events as humorous. Try and set aside the fact we're dealing with multimillion dollar assets and human lives. And feel free to laugh as no one was harmed during these tests.
These occurrences all happened before the U.S.N. came to Pratt&Whitney to request assistance.
The issue: the EPA got wind of the fact that fighter jets (and at the time, most commercial jet engines were equipped with a device called a P&D valve (pressurization and dump valve.). In its simplest explanation, when you go to start the jet engine, a valve closes allowing the fuel pump to supply fuel to the engine manifold and in turn the combustion chamber.
This is the P in the P&D valve. The engine starts and runs for however long is required and then the engine is shutdown. In the P&D Era, as soon as the fuel pump stops supplying pressure the P&D valve shuttles over to the dump side and allows all the fuel still trapped in the fuel manifolds to vent into drain manifolds then to discharge over board. (read on the ground) this caused environmentalists all over the planet to explode.
The Navy was told to cease and desist. (Always remember those communist threatening American's security)
Take a moment to digest this,while the U.S. Navy operates places other than a carrier, let's concentrate here. So every jet the Navy operates at sea now has to worry not about threats to our lives but that a cup or so of fuel dumped on deck was going to be a huge threat. Never mind that the fuel coming out is hot and it evaporates quickly, is coming out of a machine that was burning thousands of pounds per hour of this very substance and maybe there's a cup or so being expelled. Forget the fact that any fuel that was on the deck evaporated, or the deck was hundreds or thousands of miles from the nearest snail darter, and don't jump me I value nature as much or more that many, but seriously, people that are thinking up such things certainly do give credence to Mel Brooks line "Gentlemen we have to protect your phony baloney jobs."
I step off my soapbox.
That this came about put money in several people's pockets.
So the Navy, given orders to STOP dumping that fuel, set about performing that task. While this was a general order, we concentrate on the F14Tomcat.
First. The Tomcat is a pretty squat cat when sitting on the deck. The average person needs to get pretty close to the ground to be able to get under the bottom of the engine nacelles where the gang drains are. For the uninitiated gang drain manifolds all connect to a central location at or near the bottom of the aircraft these gang manifolds connect to fuel,oil,hydraulic locations around the engine to provide overboard venting to volatile fluids that weep or leak out of a location on the engine. Why? You dont want hot flammable vapors trapped inside an aircraft nacelle.
Ok folks, imagination hats on.
First attempt: F14 returning from mission. Catches the wire stops, drops wire and taxi's off to the side, engines still running. Deck hand, fresh with new orders to catch fuel before it dribbles out on the deck grabs a bucket, squats low snd runs under running F14, places bucket under gang drain and pilot given order to shut engine 1 down, remember the other engine is still running.
By now the combined engines running have spewed more fumes into the air than the dumped fuel would have contributed to planetary demise, but orders are orders, they don't have to make sense.
The pilot shuts down the number one engine and the hot fuel runs into the plastic bucket, melts through and now there’s a puddle of melted plastic and fuel on the deck. Feel free to giggle.
That test was a bust..... but undeterred and under orders the U.S.N perseveres.
This time they find a metal bucket....no melting through this time.
Same as first attempt, jet taxis over to spot where deckhand is awaiting with metal bucket. The deckhand squats to get under the spot in the nacelle where the hot fuel will be dispersed, positions the bucket in preparation for engine shutdown. Another factoid here. The fuel the Navy used at the time was JP5. Near pure kerosene with some lubricity additives. It has a flash point of 150 degrees Fahrenheit. This is to be as safe a fuel as possible aboard ship.
Compared to old JP4, approximately 50% gasoline with a flash point of -40 degrees.
Thing is, the JP5 has run through the fuel pump and into the diffuser area of the engine where temperatures regularly exceed flash point temps.
The pilot cancels engine number one, the hot fuel. A mixture of liquid fuel and fuel vapor pour into the ungrounded metal bucket and a static spark jump igniting the vapor.
A very cool headed deckhand comes running out from under the mulit million dollar aircraft, pail in hands bucket flaming away.
Pratt&Whitney given contract to fix the fuel dumping.
And so my little saga begins. Again, feel free to laugh. No one harmed in this part of the story either.
Back at the ranch a plan was devised to isolate the overboard drain pipes. There were two because there was primary and secondary fuel supplies.
The test team consisted of two engine operators (these were union guys, I NEVER touched the test stand controls in my 40+ years at Pratt)
And on this day there were two test engineers, my Senior engineer Rich and myself. Rich was an avid skydiver at this point of his life and he was laid up due to a base jumping incident a few weeks before. He and other skydiving aficioanados had flown from South Florida to West Virginia in his airplane to base jump from the New River Gorge Bridge. The state opens the bridge once a year for adrenaline junkies to plunge into the gorge between two mountains. All had been going well for the group when Rich decided he had enough time for one more jump. ImI'm not an expert on skydiving, I did make a tandem jump with Rich out of a hot air balloon but different story. I lived, but not by much.... here's what I remember. It's this open span bridge with a lot of clear space below it and nearly a thousand feet to the river. There are rescue people and boats in case you miss this little gravel bar next to the river. That your target landing spot. There are steep wooded slopes on either bank and a rail line ( this becomes important) on the right slope as you look down stream. Rich repacks hie parachute, iI think it was his 3rd or 4th of the day. He's usually very attention to detail, so maybe he was rushing to get in this last jump, maybe he was tired from the long flight up in a Cessna 182, who knows, if he did he wasn't telling.
He takes his place in line, steps up then off into empty space, throwing out the drogue chute that begins the parachute opening process. This is done to expedite the process since he was so close to impacting the planet. All goes well, initially. The drogue pulls out the main canopy it unfurls and opens....
180 degrees opposite from where he expected it. Now as the earth continues its unrelenting approach he’s facing upstream away from the gravel bar. As landing in the river starts to become a realization, he notices what may be another option. He steers towards the new location that turns out to be the railroad tracks and gravel road bed. Time has run out, decisions have been made, as he lands one of his feet(I forget which one) makes hard contact with the steel rail causing a bone in his foot to break. Next point, he was the only pilot in the group. The break was internal the medics could do little for him on site and he was forced to fly this group from West Virginia to West Palm Beach Florida. He was a hurting puppy. I include this because while we were both in the control room, Rich was occupying a corner seat, in a cast, leg elevated and was relegated to running through the steps in the program.
Since we had effectively blocked off the drain manifold, note this had to be accomplished as a temporary condition so we could return the engine to normal. The drains on the test cell were plumbed to an actual drain system.
That said, during these qualifications no fuel would actually drain. As we were at a testing facility a lot of connections were geared for testing, resulting in conditions different from actual engine configurations when installed in an aircraft. One of the differences was our ignition system had been connected to individual switches so we could simulate different scenarios. Both systems activated, the way an actual engine configuration worked, left ignitor on right off and right ignitor on left off, these simulated a normally functioning system or two scenarios where the ignition system experienced problems.
Our initial tests started with normal starts and shutdowns. We had accumulator bottles to check the drains to make sure nothing was leaking. These tests were as expected. The engine started. We then we performed a series of cold flows to simulate the engine having difficulty starting. A cold flow is where the engine rotates on the starter and the throttle is opened but the ignition is in the off position. Typically this is performed at the beginning of an engine test after overhaul or major maintenance to purge the air from the fuel system. Again, with both ignition systems functioning starts were sluggish but normal with no hung or hot start events.
Likewise the engine started a little slow on a single ignitor which we contributed to propagation of the flame around the 8 burner cans because with one ignitor the flames only had one way to go to get to all the cans. Annular burners don't experience this.
Our outdoor Florida test stands had to be equipped with noise suppressors, giant mufflers where the engines could vent their noise and not enrage the neighbors. This had gotten worse as civilization encroached on our island in the swamp. Our engine was poised in front of one of these noise suppressors a 60 ft long 10 ft diameter tube connected to a large metal box and a 90 degree deflector to turn the noise skyward.
We cold flowed the engine three times in accordance with what the Navy told us was how they conducted unsuccessful engine starts.
Motored the engine on the starter for 90 seconds with fuel flowing. This created a fuel fog that flowed out of the engine nozzle and down into the noise suppressor tube. After the third attempt fuel was dripping out all over the engine. At 90 seconds I gave the order to turn on the single ignitor.
Nothing happened, the engine continued to fog fuel down into the tube with no indication it was going to light. After maybe a minute I turned to Rich, I think to say I guess it's not going to light. Just then the control room filled with an eerie orange light, Rich's eyes grew wide as all he could see from his seat was that everything outside the control room window was orange. I quickly turned back toward the window to see the entire suppressor lit up in flames with fire coming out the vertical section. I looked quickly at the instrumentation readouts, expecting to make a callout to shut the engine down and turn on fire suppression but to my amazement the engine was running at idle with all parameters normal. We continued the remainder of the test program, wrote a report and passed the engineering change on to the USN for incorporation.
Just a day in the life.....
And if you want to learn about jet engines from someone who has been there, check out my Gas Turbine Accident Investigation course at Southern California Safety Institute, scsi-inc.com held in Redondo Beach California or arrangements can be made for me to teach at your location.
Go Back I had an amazing career.. right place, right time, and most importantly the right people. I thank you all.
Recently a friend commented to me about which aircraft I was referring to. I realized that there are those that may read this story and not remember the Grumman F14 Tomcat. I've included a picture to assist. To further help, it's the real star of the first Top Gun movie, not Tom Cruise and the hero of the Top Gun Maverick movie. When you look at the Grumman pictures of the emblem the Tomcat always has two tails. Grumman built great aircraft. Their solid designs carried naval aviators to many victories that made significant contributions to defend not only U.S. troops but defenders of many nations during the second World War. Following those traditions the F14 was an amazing airplane. Way better than it was portrayed by its detractors. (By the way, the threat imposed by U.S. fighters/ bombers to enemies of true Americans can be seen directly by how the communists in our congress limit the production of formidable deterrents.
As a bit of historical aside, the F14 had originally been scheduled for a higher thrust version of the Pratt&Whitney F100 engine designated the F401. It was a 28000 lb thrust class designation where the F100 initially for the F15 was a 25000 lb. thrust class designation. Testing on the F401 at the Pratt&Whitney Florida Research and Development Center (FRDC) in the swamplands of West Palm Beach Florida was not proceeding well. The increase in power required was proving a bit tricky and one of the main issues was the second stage turbine disk. The engine kept shedding this disk. There were stories of these disks being thrown across the test area and into the parking lot. One story was about how a guard at the post to enter the secured area once instinctively put out his foot to stop a glowing hot, liberated 2nd disk as it sped past him. Lucky for him he missed.
Not that the original F100 program was without it's faults, but maybe a subject for another time.
The U.S. Navy grew impatient that the F401 had not yet passed its PFRT (Pre Flight Rating Test) which would allow the engine to proceed to flight test.
The aircraft was proceeding at a better pace and Pratt&Whitney was placed in a bad situation. Sort of luckily, Pratt&Whitney was working with the USAF on another project, a swing wing bomber concept the F111. More stories here for another time. Pratt&Whitney offered to adapt one of the USAF engines to fit into the F14 until such time the F401 was ready for flight test.
These engines were the famous, or maybe infamous TF30's. The TF30 family were the world's first Afterburning Turbofan jet engines incorporated into fighter/bombers. Without a little research, I'm not positive which TF30 engine was the origin of the F14 engine though initially the TF30 was built in several models, the TF30-P-3, -7 and -9 and eventually the P111 in USAF F111's, though the internal design favored that the F14 TF30 came from the P3,7 or 9 family because the P111 family had an entirely different turbine design.
The TF30 also served admirably with the RAAF (Australia) and strangely Iran. Where they once again show up to save the day in Top Gun Maverick.
At one time Yugoslavia was in line to acquire some, but that never transpired. Maybe someday I can coax that story from the only person I know that may remember.
And there was also a non afterburning version the TF30-P-408 that flew in the USN Corsair.
I do ramble here but lots of history rattling around in this head.
So back to the original story.
About midway in the TF30's life in the F14, after an engine model upgrade from the P412A to the P414A I was tasked along with my senior engineer to make some "environmental " changes. Working with the design engineers we came up with some ideas and went about the decision process to pick the best candidate. From there we turned the designers loose and as they drew up the designs for the hardware changes Rich and I worked on the test plan to verify we could do what the customer requested.
Here's the story related to us, and maybe embellished a tiny bit by my imagination, but probably pretty accurate.
From this point, please try to visualize these events as humorous. Try and set aside the fact we're dealing with multimillion dollar assets and human lives. And feel free to laugh as no one was harmed during these tests.
These occurrences all happened before the U.S.N. came to Pratt&Whitney to request assistance.
The issue: the EPA got wind of the fact that fighter jets (and at the time, most commercial jet engines were equipped with a device called a P&D valve (pressurization and dump valve.). In its simplest explanation, when you go to start the jet engine, a valve closes allowing the fuel pump to supply fuel to the engine manifold and in turn the combustion chamber.
This is the P in the P&D valve. The engine starts and runs for however long is required and then the engine is shutdown. In the P&D Era, as soon as the fuel pump stops supplying pressure the P&D valve shuttles over to the dump side and allows all the fuel still trapped in the fuel manifolds to vent into drain manifolds then to discharge over board. (read on the ground) this caused environmentalists all over the planet to explode.
The Navy was told to cease and desist. (Always remember those communist threatening American's security)
Take a moment to digest this,while the U.S. Navy operates places other than a carrier, let's concentrate here. So every jet the Navy operates at sea now has to worry not about threats to our lives but that a cup or so of fuel dumped on deck was going to be a huge threat. Never mind that the fuel coming out is hot and it evaporates quickly, is coming out of a machine that was burning thousands of pounds per hour of this very substance and maybe there's a cup or so being expelled. Forget the fact that any fuel that was on the deck evaporated, or the deck was hundreds or thousands of miles from the nearest snail darter, and don't jump me I value nature as much or more that many, but seriously, people that are thinking up such things certainly do give credence to Mel Brooks line "Gentlemen we have to protect your phony baloney jobs."
I step off my soapbox.
That this came about put money in several people's pockets.
So the Navy, given orders to STOP dumping that fuel, set about performing that task. While this was a general order, we concentrate on the F14Tomcat.
First. The Tomcat is a pretty squat cat when sitting on the deck. The average person needs to get pretty close to the ground to be able to get under the bottom of the engine nacelles where the gang drains are. For the uninitiated gang drain manifolds all connect to a central location at or near the bottom of the aircraft these gang manifolds connect to fuel,oil,hydraulic locations around the engine to provide overboard venting to volatile fluids that weep or leak out of a location on the engine. Why? You dont want hot flammable vapors trapped inside an aircraft nacelle.
Ok folks, imagination hats on.
First attempt: F14 returning from mission. Catches the wire stops, drops wire and taxi's off to the side, engines still running. Deck hand, fresh with new orders to catch fuel before it dribbles out on the deck grabs a bucket, squats low snd runs under running F14, places bucket under gang drain and pilot given order to shut engine 1 down, remember the other engine is still running.
By now the combined engines running have spewed more fumes into the air than the dumped fuel would have contributed to planetary demise, but orders are orders, they don't have to make sense.
The pilot shuts down the number one engine and the hot fuel runs into the plastic bucket, melts through and now there’s a puddle of melted plastic and fuel on the deck. Feel free to giggle.
That test was a bust..... but undeterred and under orders the U.S.N perseveres.
This time they find a metal bucket....no melting through this time.
Same as first attempt, jet taxis over to spot where deckhand is awaiting with metal bucket. The deckhand squats to get under the spot in the nacelle where the hot fuel will be dispersed, positions the bucket in preparation for engine shutdown. Another factoid here. The fuel the Navy used at the time was JP5. Near pure kerosene with some lubricity additives. It has a flash point of 150 degrees Fahrenheit. This is to be as safe a fuel as possible aboard ship.
Compared to old JP4, approximately 50% gasoline with a flash point of -40 degrees.
Thing is, the JP5 has run through the fuel pump and into the diffuser area of the engine where temperatures regularly exceed flash point temps.
The pilot cancels engine number one, the hot fuel. A mixture of liquid fuel and fuel vapor pour into the ungrounded metal bucket and a static spark jump igniting the vapor.
A very cool headed deckhand comes running out from under the mulit million dollar aircraft, pail in hands bucket flaming away.
Pratt&Whitney given contract to fix the fuel dumping.
And so my little saga begins. Again, feel free to laugh. No one harmed in this part of the story either.
Back at the ranch a plan was devised to isolate the overboard drain pipes. There were two because there was primary and secondary fuel supplies.
The test team consisted of two engine operators (these were union guys, I NEVER touched the test stand controls in my 40+ years at Pratt)
And on this day there were two test engineers, my Senior engineer Rich and myself. Rich was an avid skydiver at this point of his life and he was laid up due to a base jumping incident a few weeks before. He and other skydiving aficioanados had flown from South Florida to West Virginia in his airplane to base jump from the New River Gorge Bridge. The state opens the bridge once a year for adrenaline junkies to plunge into the gorge between two mountains. All had been going well for the group when Rich decided he had enough time for one more jump. ImI'm not an expert on skydiving, I did make a tandem jump with Rich out of a hot air balloon but different story. I lived, but not by much.... here's what I remember. It's this open span bridge with a lot of clear space below it and nearly a thousand feet to the river. There are rescue people and boats in case you miss this little gravel bar next to the river. That your target landing spot. There are steep wooded slopes on either bank and a rail line ( this becomes important) on the right slope as you look down stream. Rich repacks hie parachute, iI think it was his 3rd or 4th of the day. He's usually very attention to detail, so maybe he was rushing to get in this last jump, maybe he was tired from the long flight up in a Cessna 182, who knows, if he did he wasn't telling.
He takes his place in line, steps up then off into empty space, throwing out the drogue chute that begins the parachute opening process. This is done to expedite the process since he was so close to impacting the planet. All goes well, initially. The drogue pulls out the main canopy it unfurls and opens....
180 degrees opposite from where he expected it. Now as the earth continues its unrelenting approach he’s facing upstream away from the gravel bar. As landing in the river starts to become a realization, he notices what may be another option. He steers towards the new location that turns out to be the railroad tracks and gravel road bed. Time has run out, decisions have been made, as he lands one of his feet(I forget which one) makes hard contact with the steel rail causing a bone in his foot to break. Next point, he was the only pilot in the group. The break was internal the medics could do little for him on site and he was forced to fly this group from West Virginia to West Palm Beach Florida. He was a hurting puppy. I include this because while we were both in the control room, Rich was occupying a corner seat, in a cast, leg elevated and was relegated to running through the steps in the program.
Since we had effectively blocked off the drain manifold, note this had to be accomplished as a temporary condition so we could return the engine to normal. The drains on the test cell were plumbed to an actual drain system.
That said, during these qualifications no fuel would actually drain. As we were at a testing facility a lot of connections were geared for testing, resulting in conditions different from actual engine configurations when installed in an aircraft. One of the differences was our ignition system had been connected to individual switches so we could simulate different scenarios. Both systems activated, the way an actual engine configuration worked, left ignitor on right off and right ignitor on left off, these simulated a normally functioning system or two scenarios where the ignition system experienced problems.
Our initial tests started with normal starts and shutdowns. We had accumulator bottles to check the drains to make sure nothing was leaking. These tests were as expected. The engine started. We then we performed a series of cold flows to simulate the engine having difficulty starting. A cold flow is where the engine rotates on the starter and the throttle is opened but the ignition is in the off position. Typically this is performed at the beginning of an engine test after overhaul or major maintenance to purge the air from the fuel system. Again, with both ignition systems functioning starts were sluggish but normal with no hung or hot start events.
Likewise the engine started a little slow on a single ignitor which we contributed to propagation of the flame around the 8 burner cans because with one ignitor the flames only had one way to go to get to all the cans. Annular burners don't experience this.
Our outdoor Florida test stands had to be equipped with noise suppressors, giant mufflers where the engines could vent their noise and not enrage the neighbors. This had gotten worse as civilization encroached on our island in the swamp. Our engine was poised in front of one of these noise suppressors a 60 ft long 10 ft diameter tube connected to a large metal box and a 90 degree deflector to turn the noise skyward.
We cold flowed the engine three times in accordance with what the Navy told us was how they conducted unsuccessful engine starts.
Motored the engine on the starter for 90 seconds with fuel flowing. This created a fuel fog that flowed out of the engine nozzle and down into the noise suppressor tube. After the third attempt fuel was dripping out all over the engine. At 90 seconds I gave the order to turn on the single ignitor.
Nothing happened, the engine continued to fog fuel down into the tube with no indication it was going to light. After maybe a minute I turned to Rich, I think to say I guess it's not going to light. Just then the control room filled with an eerie orange light, Rich's eyes grew wide as all he could see from his seat was that everything outside the control room window was orange. I quickly turned back toward the window to see the entire suppressor lit up in flames with fire coming out the vertical section. I looked quickly at the instrumentation readouts, expecting to make a callout to shut the engine down and turn on fire suppression but to my amazement the engine was running at idle with all parameters normal. We continued the remainder of the test program, wrote a report and passed the engineering change on to the USN for incorporation.
Just a day in the life.....
And if you want to learn about jet engines from someone who has been there, check out my Gas Turbine Accident Investigation course at Southern California Safety Institute, scsi-inc.com held in Redondo Beach California or arrangements can be made for me to teach at your location.