why is my vnav 1 hour and 15 minutes but my ete is 2 hours and 4 minutes?
your VNAV is your TOD (time of Descent into the airport), while the ETE is the estimated time you arrive at the airport. A large difference can be a long decent and/or wind
I would check out this tutorial. It explains the VNAV features in great detail, letting you know of anything you need to about VNAV.
I would also recommend checking out the User Guide. A helpful tool for even the most experienced pilots, it would definitely help you out with some of the queries you have.
I’ll link you the VNAV section of the user guide, I would give it a read. It has very helpful videos, references, and guides to assist you through the descent phase of your flight.
From the User Guide:
Top of Descent, also known as TOD; is the point at which you initiate a descent from cruising altitude to another altitude in preparation for the arrival phase of flight. TOD is displayed in time and distance can can be found in two places, these are:
That’s the time you’ll take from where you currently are, to reach the point from which you start descending from cruise.
That’s your “expected time enroute” aka how long it’ll take you to reach your destination.
Bc you have 1 hour and 15 minutes until you descend but 2 hours 4 min until you land
but that’s a massive time difference?
Yep. It’ll take you 49 minutes to descend to your destination.
This could be because of various factors - your cruising altitude, winds, airspeed, etc.
look at my post above. More info would be needed if you think this is a problem with calculations
Refer to @Pingu ‘s post above; it had all the necessary information you seek, as well as the User Guide, which can help answer many future questions
Here’s a real-world example of the TOD being much different from the time of arrival. Let’s use UA1992 as an example. The flight is a standard, one hour flight from Newark to Washington. According to flightaware.com, the flight began only 20 minutes into the flight, leaving 40 minutes for descent.
Aircraft slow down during descent, making the estimated flight time longer. Climbing the aircraft is much quicker, as speed is being gained, rather than lost. Though climb to cruising altitude may only take 5-10 minutes, this is because vertical speed is maintained much higher than during descent. Aircraft during the climb often go 2500+ feet per minute, while aircraft during the descent often go anywhere from -500fpm to -2500fpm. Not only that, but many STARs and approaches often have altitude and speed restrictions to comply with noise abatement and/or airspace restrictions. Overall, the descent time of an aircraft is going to have a large time gap between the Top of Descent (TOD) and the estimated time of arrival due to speed, descent speed, and winds.
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