TF-30 detuned

[captain_dalan]

Hey guys, this post isn't directly related to the HB module, so if a mod thinks it should be moved, feel free to do so.

Anyway, a while back we had this discussion on the TF-30's performance, or to be specific it's static installed thrust as listed in the F-14 manuals and it's thrust as listed in some brochures. The difference was largely explained as loss of air due to intake geometry and bleed air, but a few of us seemed to recall that at some very early point in the development, the engine was also detuned. However, we could not find any sources on the topic and the earliest official documentation we had, appears to indicate that the engines were always rated as such (about 17000lbs in AB). None of the sources i though i read about the detuning  were available to me personally anymore, so i started to think i may be imagining things.

And here comes this video that I just watched. These gentlemen flew on the 2nd cruise of VF-1, so that dates them 1975-1976 IIRC, and they do mention that during their introduction to the plane, they flew them clean (as in no external tanks) and with the engines tuned for higher performance. They also mentioned they soon after that, the engines were tuned down. The exact date was not mentioned, but from the context of the interview i assume it was no later then 1977-1978. 

Here it is, i hope you enjoy it. I most certainly have, maybe as a result of my bias. After all this is my favorite F-14 era  
 

  

[jcdata]

Defined because of the compressor blowing out IMHO..I think engine series 412 fixed the issue with stronger band and compressor..


Going by memory and research...

Sent from my SM-G998U using Tapatalk

[captain_dalan]

Yeah, but the engines it seems, stayed tuned down for the rest of the service. I could never figure out if it was safety due to potential structural failure or due to operation/airflow failure. 

[SgtPappy]

19 hours ago, jcdata said:

Defined because of the compressor blowing out IMHO..I think engine series 412 fixed the issue with stronger band and compressor..


Going by memory and research...

Sent from my SM-G998U using Tapatalk
 

Yea, I believe the -412A was that mod and then came the -414 sometime in 1977 and the -414A in 1984 which was reportedly much better but still not up to the standards of the late 80's digital EEC-equipped engines. AFAIK they all were trimmed at the same levels by the time the -414 was widespread in the F-14 fleet.

 

I've heard some pilots (there's a video on youtube of an airshow Tomcat crew in 1997) even state that the engine was detuned to ~17,000 lbf thrust because they're quoting the installed thrust value from the manual and comparing it to the brochure uninstalled static thrust (the ~20,800 lbf value). Pretty confusing.

Edited October 1, 2021 by SgtPappy

[Quid]

I've heard this a number of times, but based on the various NATOPS entries, it doesn't seem to be right.  It has to do with what SgtPappy mentions - installed thrust vs. static uninstalled thrust.  Even the PTO from 1972 lists the installed thrust as 17,000 lbs (it's actually a typo that says "1700" - pg. 1-28).  The 1975 NATOPS, which also predates engine updates, also provides 17,000lbs installed static thrust for maximum AB, and 11,700 for min for the TF-30P-412 (pg. 1-39).  The 1981 and beyond versions, which list the TF-30P-414 or 414A, provide 17,077lbs installed thrust (a negligible increase, rather than a decrease in thrust, pg. 1-13 for the 1984 Change 1).  As SgtPappy points out, the 20,800lbs value is uninstalled.

 

It shouldn't need to be said, but because every time anyone leaves out any detail, it seems as though the "ackshually" army (of which I admit I am sometimes a part) gets a notification: this is of course at 0 altitude and airspeed installed.  Yes, the TF-30 will achieve 28,000lbs per engine at .9M at sea level according to open-source publications (e.g., Stevenson's Grumman F-14), and thrust is highly dynamic dependent on altitude and airspeed (dynamic pressure), etc., etc.

Edited October 1, 2021 by Quid
Grammar, amplification

[captain_dalan]

Well that's where all the confusion came about. Lack of mention in official sources. And yet, it keeps popping out. It's unfortunate that less and less people remain of that era that can provide accurate accounts. 

[SgtPappy]

7 hours ago, Quid said:

I've heard this a number of times, but based on the various NATOPS entries, it doesn't seem to be right.  It has to do with what SgtPappy mentions - installed thrust vs. static uninstalled thrust.  Even the PTO from 1972 lists the installed thrust as 17,000 lbs (it's actually a typo that says "1700" - pg. 1-28).  The 1975 NATOPS, which also predates engine updates, also provides 17,000lbs installed static thrust for maximum AB, and 11,700 for min for the TF-30P-412 (pg. 1-39).  The 1981 and beyond versions, which list the TF-30P-414 or 414A, provide 17,077lbs installed thrust (a negligible increase, rather than a decrease in thrust, pg. 1-13 for the 1984 Change 1).  As SgtPappy points out, the 20,800lbs value is uninstalled.

 

It shouldn't need to be said, but because every time anyone leaves out any detail, it seems as though the "ackshually" army (of which I admit I am sometimes a part) gets a notification: this is of course at 0 altitude and airspeed installed.  Yes, the TF-30 will achieve 28,000lbs per engine at .9M at sea level according to open-source publications (e.g., Stevenson's Grumman F-14), and thrust is highly dynamic dependent on altitude and airspeed (dynamic pressure), etc., etc.

 

Indeed, and Bio, who we all love, has specifically quoted the same mistake in OP's video stating that the detune from 20,000 lbf in the enthusiast books to 17,000 lbf in the NATOPS was a "big hit" to engine thrust. These guys obviously know what they're talking about, but engineering-level mistakes like this that don't actually concern the crew are made even by the best pilots/RIOs. After all, they're more concerned about turn rates, speeds, climb profiles, TSFC etc. and the engine thrust curve is just extra trivia since that value is unseen and is baked into the performance parameters that actually matter to them. 

Edited October 2, 2021 by SgtPappy

[Scrape]

There's an aspect to engine performance in fighters that's often considered.  Tuning is done more often than people think, by which I mean daily or near to.  An engine is tuned for a particular mission condition, and this is often done without pilot input or knowledge.  The sortie/mission dictates the tuning.  Mission says the pilot will be performing high altitude CAP?  An engine tune is set for that.  Next mission the jet will be loaded with snake eyes?  He'll be low level then, and a tune is loaded for that.  Like a racecar before a race, mechanics tune the engine for that particular track.  Fighter engines are the same way.  Data is analyzed after the flight and the tune is either kept or adjusted.  This can greatly affect performance output in addition to atmospheric variables and other factors.  This can also vary pilot accounts of what their engine was able to do when and how much power is made.   This is the way it is currently and has been for the last couple of decades.  I can't imagine it being much different during the days of the Tomcat.

[Victory205]

Afraid not. Didn’t happen in the days of hydro mechanical fuel controls, and likely doesn’t happen now due to the requirement for expensive, labor intensive engine runs for verification. 

Engine thrust levels do vary between motors, as a result of the differences in fuel control setups, acceptable ranges, and overall wear. We used different fuel types between shore and ship based too.

[captain_dalan]

5 hours ago, Victory205 said:

Afraid not. Didn’t happen in the days of hydro mechanical fuel controls, and likely doesn’t happen now due to the requirement for expensive, labor intensive engine runs for verification. 

Engine thrust levels do vary between motors, as a result of the differences in fuel control setups, acceptable ranges, and overall wear. We used different fuel types between shore and ship based too.

Roughly speaking, purely academically speaking, how much of an effort it is? And does it involve full engine removal? 

[cheezit]

1974- and 1977-dated copies of NAVAIR-00-110AF14-1 ("Standard Aircraft Characteristics Navy Model F-14A Aircraft") list "static thrust at sea level" of the TF30-P412A in Max A/B as 20,900 lbs per engine.
 

As mentioned earlier in the thread, the 1972 preliminary NATOPS says "At sea level, static conditions, each [TF30-P412] engine develops 10,500 pounds installed thrust at military and 1700[0] pounds thrust at maximum afterburner."

 

I wonder if ambiguity about the word 'static' is part of the confusion - it's ambiguous (at least to an ignorant non-pilot such as myself) whether it implies 'uninstalled' or whether 'static/moving' and 'installed/uninstalled' are orthogonal, and thus it's unclear whether a phrase like 'static thrust' means 'installed but at zero airspeed' or 'in an immovable [aka static] test fixture' if installed/uninstalled isn't explicitly stated.

 

 

[SgtPappy]

4 hours ago, cheezit said:

1974- and 1977-dated copies of NAVAIR-00-110AF14-1 ("Standard Aircraft Characteristics Navy Model F-14A Aircraft") list "static thrust at sea level" of the TF30-P412A in Max A/B as 20,900 lbs per engine.
 

As mentioned earlier in the thread, the 1972 preliminary NATOPS says "At sea level, static conditions, each [TF30-P412] engine develops 10,500 pounds installed thrust at military and 1700[0] pounds thrust at maximum afterburner."

 

I wonder if ambiguity about the word 'static' is part of the confusion - it's ambiguous (at least to an ignorant non-pilot such as myself) whether it implies 'uninstalled' or whether 'static/moving' and 'installed/uninstalled' are orthogonal, and thus it's unclear whether a phrase like 'static thrust' means 'installed but at zero airspeed' or 'in an immovable [aka static] test fixture' if installed/uninstalled isn't explicitly stated.

 

 

The way I understand it is that "static" and "installed" indeed orthogonal terms. I'm not sure I've ever heard "static" implying "installed" in the industry. 

 

Static conditions are, as you say, on a stand with zero freestream velocity at the inlet. This is obviously a practical condition to test on the ground. I would think installed should be explicitly stated.

[captain_dalan]

On 10/4/2021 at 4:20 PM, cheezit said:

1974- and 1977-dated copies of NAVAIR-00-110AF14-1 ("Standard Aircraft Characteristics Navy Model F-14A Aircraft") list "static thrust at sea level" of the TF30-P412A in Max A/B as 20,900 lbs per engine.
 

As mentioned earlier in the thread, the 1972 preliminary NATOPS says "At sea level, static conditions, each [TF30-P412] engine develops 10,500 pounds installed thrust at military and 1700[0] pounds thrust at maximum afterburner."

 

I wonder if ambiguity about the word 'static' is part of the confusion - it's ambiguous (at least to an ignorant non-pilot such as myself) whether it implies 'uninstalled' or whether 'static/moving' and 'installed/uninstalled' are orthogonal, and thus it's unclear whether a phrase like 'static thrust' means 'installed but at zero airspeed' or 'in an immovable [aka static] test fixture' if installed/uninstalled isn't explicitly stated.

 

 

I have almost completely forgotten about the SAC's, and yes they do state 20900lbs of thrust. Thanks for the pointer. 

[captain_dalan]

On 10/4/2021 at 9:01 PM, SgtPappy said:

The way I understand it is that "static" and "installed" indeed orthogonal terms. I'm not sure I've ever heard "static" implying "installed" in the industry. 

 

Static conditions are, as you say, on a stand with zero freestream velocity at the inlet. This is obviously a practical condition to test on the ground. I would think installed should be explicitly stated.

BTW, both sources, the SAC and the Flight Manual, state their thrust values as static, not installed, even though one quotes 20900 and the other 17000. 

[Quid]

1 hour ago, captain_dalan said:

BTW, both sources, the SAC and the Flight Manual, state their thrust values as static, not installed, even though one quotes 20900 and the other 17000. 

The FM does indicate installed. 

The PTO says: "At sea level static conditions, each engine develops 10,500 pounds installed thrust at military and 1700[0] pounds thrust at maximum afterburner." (1-28)

The 1975 revision removed this section, then mentioned the thrust in a later part specifically for afterburner augmentation (Zone 1 through 5), which says: "Thrust augmentation can be modulated between 11,700 pounds and 17,000 pounds installed net thrust at static sea level conditions." (1-39)

From 1981 and until 2004, the thrust section is quoted as: "The installed engine thrust at military and maximum afterburner power is 10,875 and 17,077 pounds, respectively." (1-13; 1981, 1984, 2-10; 1997, 2-9; 2004).

 

That said, I could still see where there is potential for confusion, because it also says in the early manual both "static" and "installed."  I take this to mean installed thrust at 0 altitude and 0 airspeed, such as with the aircraft on the catapult in Zone 5.  When the number is quoted as just "static" and showing 20,800 pounds, it would be uninstalled (i.e., 0 altitude, 0 airspeed, mounted for a test).

Edited October 9, 2021 by Quid
Clarification

[SgtPappy]

1 hour ago, captain_dalan said:

BTW, both sources, the SAC and the Flight Manual, state their thrust values as static, not installed, even though one quotes 20900 and the other 17000. 

Apologies if I misunderstand you but static and and installed are not mutually exclusive terms. They way I sometimes think of it is how a car can be mate black but just because it's matte doesn't mean its black.. it could be matte red or shiny and black. Silly example but I hope you get the point. Shiny and colour are two different dimensions that don't rely on each other as are installed and static thrust.

 

Static just means the engine isn't moving. It may or may not be installed in the aircraft. Quid's excellent post above should remove any remaining ambuguity.

[captain_dalan]

On 10/9/2021 at 8:23 PM, SgtPappy said:

Apologies if I misunderstand you but static and and installed are not mutually exclusive terms. They way I sometimes think of it is how a car can be mate black but just because it's matte doesn't mean its black.. it could be matte red or shiny and black. Silly example but I hope you get the point. Shiny and colour are two different dimensions that don't rely on each other as are installed and static thrust.

 

Static just means the engine isn't moving. It may or may not be installed in the aircraft. Quid's excellent post above should remove any remaining ambuguity.

Of course not, nor was it meant to sound that way. Purely pointing out to the semantics, that is the choice of expression