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Newbie Joined: May 26, 2006 Posts: 8 Status: Offline

Hi to all!
In -1, it is claimed that although SEC is secondary mode, there is nothing to worry about as it is as safe as PRI mode.
However I (and most of Turkish Pilots) don't think so nowadays. This last incident is one of the reasons for us to believe so. Upto now, TUAF has lost at least 10-15 Vipers due to SEC problem. Most of them were auto SEC transfer resulting with flameout. Even -1 says "land as soon as practical", these incidents made us believe that we have to land ASAP.
What do you think of it? Is SEC mode really safe?

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I wouldn't change reg's to make it a code 2 flyable condition or anything... It does serve as a better back-up than some other hydrazine based systems, that shall remain nameless. Evil or Very Mad

SEC works a bunch better than the old BUC system. Now THAT was a scary system!

Elite 1K Joined: Apr 26, 2004 Posts: 1215 Status: Offline

Mark is 100% correct.

It's not SEC that's unsafe, it's what got you into SEC. The best backup mode in the world won't help a totally trashed engine.

Best Regards,

My two cents, SEC mode is always safer than losing the only engine you got. But treat it as if it was something serious and hurry up and land. The engine specialist will tell you if it was something serious or not. I could be be something as simple as a rigging problem or so.

SEC mode is almost as reliable and stable as PRI mode. It is safe, and very effective.

SEC mode is as reliable as the fuel-control systems on J57s, J75s, or J79s All had good control systems, but still had their mechanical limitations. I would bet the SEC on an F100 or F110 is a more reliable system than many of those turbojets.

Exclamation

Personal opinion time...

Unlike what the -1 calls for, (talking F100 now) I would never manually select SEC. As we all know SEC is a "Hydro-mechanical backup" to PRI which is a "Digital Electronic Feedback" System.

I'd much rather have the computer help keep the engine running if I had problems. With all it's logic, fault accommodation, redundancy, it is more likely to address any "issues" with the engine, while the pilot addresses the problem of "getting down." I know it's hard to trust computers in situations, but newer engines such as the F119 have 2 computers (from what one can see on published photos) and may not even have a "hydro-mechanical backup"

I know pilots can't/won't do this because of the way emergency procedures are written, but the DEEC on an F100 will accommodate most issues and adjust the engine accordingly to maintain limits. (All done without pilot intervention) There are multiple levels of fault tolerance built into the system and numerous backups to sensor inputs and control outputs.

Now if the engine transfers to SEC on it's own. You have a BIG issue with the engine. The computer is telling you it can't or won't control the engine safely anymore. Then you should throw the SEC switch and find a hard flat surface with the proper dimensions, use it and call an engine guy....

We shouldn't forget the F-16 is the safest single engine jet fighter of ALL TIME! (SEC mode included........) Wink

Quote:

Most of them were auto SEC transfer resulting with flameout.

Sir, I think what you stated is backwards ... I think the motor transfered to SEC trying to rectify the impending flameout. If a mechanical anomoly exist to cause a flameout ... PRI/SEC ain't going to help!

If data is recoverable from the smoking holes ... what PFLs/MFLS/EVENTS/Transient Data/ were downloaded?

JoeSambor wrote:

It's not SEC that's unsafe, it's what got you into SEC. The best backup mode in the world won't help a totally trashed engine.

I believe this statement from Joe is the key to this topic Idea

During a serious engine malfunction the engine's control system will try to "accommodate" the problem before transferring to SEC. The "Auto Transfer to SEC" is a last resort of the engine's control system to salvage usable thrust.

If there is something THAT wrong, SEC becomes almost a mute point...

Enthusiast Joined: Mar 14, 2004 Posts: 40 Status: Offline

Isn't advised to position in auto transfer situation the switch also to sec during the rest of the flight? It was told to me by my engine run instructor to do so during engine run

jetfuelstarter wrote:

Isn't advised to position in auto transfer situation the switch also to sec during the rest of the flight?

Yes, you wouldn't want the engine trying to switch back and forth. It could cause the engine to end up in neither mode and not operate at all...

Well, if you had a auto SEC trans on a ground maintenace run, you would think you would want to shut down. A curious person would have the B-man download it and cycle the switch to see if it clears. If you got a hard fault that told the DEC to stand down and let the MEC take over, you would think it would not matter if you didn't hit the switch (for maintenace personnel only) cause it is an auto trans and the switch is ruled out. If it auto trans wewther is was an ESDC takinng a s#!t or whatever, never seen itself trying to automatically go back into Pri without a restart. TEG or JFS, where do you see that it says in our FI's, cause it is not in our JG's, about switching to Sec if you had an auto trans?

Mushmouth wrote:

If you got a hard fault that told the DEC to stand down and let the MEC take over, you would think it would not matter if you didn't hit the switch (for maintenance personnel only) cause it is an auto trans and the switch is ruled out. If it auto trans whether is was an ESDC takinng a s#!t or whatever, never seen itself trying to automatically go back into Pri without a restart. TEG or JFS, where do you see that it says in our FI's, cause it is not in our JG's, about switching to Sec if you had an auto trans?

It doesn't matter to ground maintenance, but does if you're out flying. I don't believe it is in the FIs but is in the -1.

It's a Pratt thing... If the engine auto-transfers due to a MFC mode solenoid fault, the engine's MFC may try to shuttle back and forth from PRI to SEC if the switch is still in PRI.

On a Pratt it can cause a loss of mode condition for the MFC where it doesn't know if it is in PRI or SEC. That is why Pratt tech data calls for Mode "SEC" after an auto-transfer.

During a specific "Class-A" mishap, an engine transfered to SEC, but the pilot had left the switch in PRI. The engine then decided it wasn't in any mode, and quit on the job...

New step added to the -1!

Ahhh!!! I gotcha. It's a Pratt thing. Or is it that Pratt is just a piece of crap?? Just kidding with you TEG. I give my troop crap all day cause he is a Pratt guy. Thnx

Mush

Seen this the other day (Ground abort) … During engine start {750 a Nellis POS loaner (Pratt) ) JFS off, Generator just came on line … NOZZLE SLAMED SHUT? No SEC lite no nothing.

Called Engine Groupies out … No bit-ball no fault on the download? WTF?

Grabbed a run screen fired her up an the same (nozzle hard closed) … real time CEDS said nozzle @ 91% but cockpit indicator said nozzle @ 0, and nozzle was closed?

Thoughts

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Is SEC mode really safe?