ForeFlight Performance Profiles

[RossG2000]

Greetings all,

I upgraded my ForeFlight to the performance version and that comes with built out performance profiles for aircraft that they claim is directly from the owners manual or operating standards for each aircraft applicable. I have a C172, H model, and the performance profiles don't tell me what speeds they're utilizing for the given RPM, etc. Knowing the IAS it's calculating flight time at is helpful. When I looked up in the ForeFlight guides, it shows a screenshot of the Performance Profiles and there's a section that shows the IAS they're basing the cruise profile off of, for example. Mine do not show that. All I get to do is drag a bias slider to adjust the profile's settings up or down by a percentage I choose. Not very helpful.

When I build a "basic" or "custom" aircraft profile, I specify the airspeeds myself.

Does anyone know if this is how it is supposed to be? I attached a screenshot of what I see (sliders) and what the PDF instruction manual shows I should see (obviously, different aircraft).

Thank you.

 

[wyattgrubbs]

I’m having the exact same problem I typically descend at 90 kts and 2000 rpm and it refuses to let me adjust it have you found a solution?

 

[RussR]

Greetings all,

I upgraded my ForeFlight to the performance version and that comes with built out performance profiles for aircraft that they claim is directly from the owners manual or operating standards for each aircraft applicable. I have a C172, H model, and the performance profiles don't tell me what speeds they're utilizing for the given RPM, etc. Knowing the IAS it's calculating flight time at is helpful. When I looked up in the ForeFlight guides, it shows a screenshot of the Performance Profiles and there's a section that shows the IAS they're basing the cruise profile off of, for example. Mine do not show that. All I get to do is drag a bias slider to adjust the profile's settings up or down by a percentage I choose. Not very helpful.

When I build a "basic" or "custom" aircraft profile, I specify the airspeeds myself.

Does anyone know if this is how it is supposed to be? I attached a screenshot of what I see (sliders) and what the PDF instruction manual shows I should see (obviously, different aircraft).

Thank you.

You're using the performance setting for "max rpm, lean mixture", so it's just using the numbers off the performance chart in the POH that pertain to that configuration at whatever altitude you select. So if you select 5000 as your altitude, it's using 2700 rpm, 87% power, 136 mph TAS, 9.8 gph.

Whether you can or should actually fly at this setting is debatable. But if you look at the other options, such as 2500 rpm, the same basic idea applies. You go to the performance chart and it says at 5000, 124 mph, 7.9 gph. At 2500, 125, 8.5. And on like that.

The bias values allow you to adjust for your known reality. If you know that at 2500 rpm at 5000 you really only do 120 mph TAS, then you set the speed slide to -3.2%. If this burns 8.5 gph, then you set the other slider to +7.5%.

Foreflight can only go off of what is in the POH. Some POH/AFMs are much more detailed than others, and the performance charts reflect that.

 

[RussR]

I’m having the exact same problem I typically descend at 90 kts and 2000 rpm and it refuses to let me adjust it have you found a solution?

I don't see ANY information on descent in the 172M Owner's Manual (should be owner's "pamphlet"). So who knows what they're using. In this case, I'd just assume cruise power setting and fuel flow to the destination, then you know you'll be overestimating.

But you slow down for descent? Why? I'd at least fly cruise speed, backing the power off as necessary to maintain it in the descent.

 

[midlifeflyer]

But you slow down for descent? Why? I'd at least fly cruise speed, backing the power off as necessary to maintain it in the descent

I see a lot of that, mostly with newer pilots. I do a lot of transition training with my flying club and since it’s often transition to a G1000, I include a cross country flight. “Do you really want to fly this slow for the next 25 miles? Is this why you want to fly a 130 kt Diamond instead of a 110 kt Cherokee? So you can go slow?” is a common question I ask.

I think it’s about too much practice area, not enough cross country.