I had a CP tell me that you could only call in fatigued for feeling due to lack of sleep the night prior. In other words, I couldn't call in for chronic fatigue...

But, to the OP. I can usually bang out 5 legs in a 12 hour day and feel fine. Then again, doing the same legs to the same midwest cities to the same hub can get fatiguing in its own way. It's why I don't mind a thunderstorm to dodge or a delay to take just to mix things up a bit.

Thanks. I wasn't necessarily asking for permission to call in fatigued, but wanted to now how others gauged their level of fitness for duty.
I've just heard it said, "if you're tired, call in." I didn't think that was super helpful or descriptive.

Pilot pushing.

Now the company may have pay policies (we do) such that if you call in fatigued on day two of a four day because...

A. You had acute fatigue because you didn't sleep that night due to the hotel being too loud/hot/cold. etc you would get paid for the missed flying.

B. You had chronic fatigue because you had a baby at home and didn't sleep much in the week prior to coming to work...not getting paid.

Don't specify acute or chronic fatigue if you call in. The company can ask for details about why you're fatigued, but if they don't like your answer they cannot force you to fly. Once you drop the "F Bomb" the FAA now requires that you be removed from duty, no negotiation, discussion or pushback. If they push you, call your CMO...they'd love to hear about it.

You know yourself, you have to make the call.

Not a morning person here, really early shows are not going to find me at my best. I will not feel as chipper as I do at 1100, but I know that if I have some coffee and proceed methodically and slowly by the time we're ready to start moving I'll have perked up. But if I no-kidding actually feel sleepy at that point, it's a no-go.

For some people feeling sleepy may not be the same as fatigued, it's impossible to clearly define as it's on a spectrum. The FAA allows schedules which are clearly out of whack with circadian rhythm so they can't expect you to be at the top of your game. You have to assess where you are on the scale and make the call.

Even if you don't feel fatigued, there are times you should call in to CYA...say the commute went horribly wrong and you spent all night sleeping in terminals or airplanes instead of a crashpad. If something bad happened on one of your flights, the NTSB and FAA would assume you were fayigued.

If you're "tired" from reroutes, you're not tired, you just don't like your job. When you were new, it didn't matter if they DH you 3 times acrosss the country you were just happy to be there. Remember? If not the jobs not for you.

Yeah, no. So I dead head to Denver from Detroit, after I'm supposed to be back the night before. Flight cancels at 2 in the morning, spend 45 minutes trying to get a hotel. Finally get there at four only to have to go back the next day, but don't worry we just put an hour of ready on your schedule back in Denver. Land with a voicemail on my phone, hey you're going to (insert some place) tonight. It doesn't leave for three and half hours. Four hours later the rest of the crew is stuck at an out station. Seven hours after I got to Denver we leave and I land after I've been extended with a 15:45 duty day. But being rerouted isn't exhausting at all.

You can be entirely willing to work and still be unfit for duty...

??????????

Haha. Exactly. If you're fatigued you're fatigued. Call in. It's the professional thing to do.

Thing with my company is, (maybe others/all?), they don't want to hear "I think im going to be fatigued if I do this flight". Either you are fit for duty or you are not. This has bit me in the ass before when I found myself having no business being in the flight deck 1/2 way through a 2 hour plus leg.
So, when I call in now, it is "I AM fatigued" and I am removed from duty.

I only called out fatigue one time... Approaching 15th hour duty waiting for metar to improve from vv001 with gusty winds at night at overnight destination... I didn't want to become subject of training videos.