Flying characteristics of 172N with backseat pax

RyanB

RyanB

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I am a 70 hour PP and have not had someone ride backseat, yesterday i took a friend up and she asked if her friend could come to, i said because i haven't had enough time with pax in the backseat id rather not. I weigh 140 roughly and she weighs about the same and her friend about the same. How would the flying characteristics of the 172N 160hp change with a 140lb person in the backseat and 2 140lb people up front? Would the plane fly noticeably different like especially at critical phases of flight or about the same? Thanks
 
Same as flying with a full fuel load as opposed to a light fuel load. As long as the W&B checks you're good. Probably the only thing you will notice is a longer ground roll and lower climb rate.
 
I know i would be within limits with that amount of weight, i just wonder how he cg and flying characteristics change
 
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In my limited experience, weight being the same, the 172n flies better with more aft cg. As I have approached max gross I've noticed that my go around tend to climb crappier and might even touch down depending on when I decide to go around. Just keep the nose down a bit, build airspeed, milk up flaps to 10, and wait for it to climb without trying to force it :)

If you feel the least bit apprehensive, get a CFI to fly with you with someone in the back near max gross. It is a good, safe learning experience.
 
ChrisK said:
In my limited experience, weight being the same, the 172n flies better with more aft cg. As I have approached max gross I've noticed that my go around tend to climb crappier and might even touch down depending on when I decide to go around. Just keep the nose down a bit, build airspeed, milk up flaps to 10, and wait for it to climb without trying to force it :)

If you feel the least bit apprehensive, get a CFI to fly with you with someone in the back near max gross. It is a good, safe learning experience.
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That is what i have thought about doing as well, for now i plan to just have one pax
 
I didn't expect that our new pilot friend wasn't doing a weight and balance. If you've only ever flown the plane underweight with forward CG, this is a fine question to ask even having read the POH and run the weight and balance numbers.
 
ChrisK said:
I didn't expect that our new pilot friend wasn't doing a weight and balance. If you've only ever flown the plane underweight with forward CG, this is a fine question to ask even having read the POH and run the weight and balance numbers.
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I usually dont do a wb if im only flying with one pax well under gross weight, if i had more than one pax and different fuel loads i would do a wb for sure, not what i meant, its always a good idea to do a wb. Thank you
 
Ryanb said:
That is what i have thought about doing as well, for now i plan to just have one pax
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Baby steps. Among my first 172 pax were folk who weighed almost 300 lbs. I was at 200 at the time, so our CG was pretty out of whack. I didn't fly a 172 at gross until I had about 200 hours and it was an eye opening experience on landing. Fortunately it was a cold, cold day. Unfortunately it was blustery.
 
ChrisK said:
I didn't expect that our new pilot friend wasn't doing a weight and balance. If you've only ever flown the plane underweight with forward CG, this is a fine question to ask even having read the POH and run the weight and balance numbers.
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Never implied that he didn't run the numbers.

If you didn't feel comfortable doing it, by all means...don't do it. I would have figured adding another girl to the experience would have brought the comfort factor up. If that didn't do it, you could always shave off 10-20 gallons.:D
 
Gucci Pilot said:
Never implied that he didn't run the numbers.

If you didn't feel comfortable doing it, by all means...don't do it. I would have figured adding another girl to the experience would have brought the comfort factor up. If that didn't do it, you could always shave off 10-20 gallons.:D
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Hah. My instructor weighed about 250. With me at 200 I have no clue how we legally flew in a 152. We often left with 15 gallons or less.
 
My older 172 has the gross weight increase and we have gotten pretty close to limits on it (4 people, full fuel) - it handles fine, as long as you're within CG you probably won't notice a difference...if you're concerned, carry a little extra speed in the pattern and take up some more runway to build in some extra margin.
 
Gucci Pilot said:
Never implied that he didn't run the numbers.

If you didn't feel comfortable doing it, by all means...don't do it. I would have figured adding another girl to the experience would have brought the comfort factor up. If that didn't do it, you could always shave off 10-20 gallons.:D
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LOL, its not that i didn't want to take her, i just felt for my comfort level and safety i better off not have her come.
 
You'll be fine, don't worry about it, you'll climb slower. It'll land so close to "the same" that it's no worries.

If you're really worried grab an instructor and stick a friend in the back seat. That said, as an instructor, unless I knew someone was an incredibly poor pilot, I would tell them not to waste their time and money.
 
I agree that it is a great question but the statement made got me to thinking and prompted my response. I personally think that the plane handles better with more weight, climb performance being what it is.
 
Ryanb said:
I usually dont do a wb if im only flying with one pax well under gross weight, if i had more than one pax and different fuel loads i would do a wb for sure, not what i meant, its always a good idea to do a wb. Thank you
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Bad habit.

It won't matter in a typical 172, but some airplanes in that class will have excessively forward CG with two up front, and need ballast. You'll wonder why the airplane is such a bear to land.

Some 177s and 182s with full fuel, for instance.

Engine STCs tend to lop off allowable forward CG as well, though even the 180 HP 172N's don't seem to be excessive.
 
Geez you and your friends are not heavy.enough :) It is going to be fine.
Everyone I know (males) is like 200-240 That makes a HUGE difference in the way our plane feels. Frankly it is a pain in the ass to fly with a heavy guy in the back.

I doubt throwing another 140 in the back seat is going to cause enough of a change in a 172 to cause you much more stress.

I would just do it. If it concerns you just plan for a lap around the pattern.
If you are really concerned, have the CFI in the right seat but I think you will be surprised how little it changes.

I had me (190) my instructor (~190) and friend (~230) in the back seat in a 172 and I could tell he was back there but it wasn't bad at all.
 
You may notice a slight difference,but with the weights you describe,it's a non event.as the rear pax get heavier,you will notice the change.
 
You'll be fine, just don't spin it. The 172 is approved for intentional spins with one or two up front but with somebody in the backseat it isn't.
 
If you've never done it before I think you'll find that the 172 flys and handles much nicer with someone in the back seat. Might even go faster.
 
Flymeariver said:
Why would that be?
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One of the inefficient things about traditional airplanes is the fact that the tail has to push DOWN to offset the wings pushing up. Generating lift towards the ground isn't ideal with an airplane that you want to go up. The further you can push the CG back, the less the tail has to generate lift towards the ground, the faster and more efficient you will be.

I always try and load things to push the CG as far aft as I can (while respecting the W&B envelope).
 
Ahh, I understand, thanks for letting me kinda derail his thread. Perhaps I'll have to grab a 2nd pax and try this out :).
 
Gucci Pilot said:
Same as flying with a full fuel load as opposed to a light fuel load.
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I wouldn't say that. You're going to have noticeably lighter pitch forces and lower pitch stability, and that is particularly significant for takeoff, landing, and slow flight/stalls. Personally, I include at least once around the pattern (preferably some maneuvers in the practice area and several takeoffs and landings) with enough in the back to be close to aft cg limit during primary training in a 4-seater or 4-seat transition training for someone with only 2-seat experience.
 
peerlesscowboy said:
With the CG farther aft there's less enery wasted on holding the the tail down. OTOH I suspect the added weight would cancel any benefit out?
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Depends on how much weight how far back in what airplane. Friend of mine who races his Grumman Tiger did the flight testing and found he can get a knot or two more with just the right weight in just the right place. And in those races, a knot or two can make a big difference.

BTW, he will not share the exact information, lest his competitors be able to reduce his competitive edge.
 
Ron Levy said:
I wouldn't say that. You're going to have noticeably lighter pitch forces and lower pitch stability, and that is particularly significant for takeoff, landing, and slow flight/stalls.
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A 10,000 hour CFI may notice that but I doubt a 70 hour PP will.
 
I've filled up all the seats in a 172N. It definitely feels heavier and a little more whale-ish on the controls. Just make sure you do the W&B. I took my mom and friend up for some lunch and my mom said she wanted to bring a friend also and it turned out to be my pastor's wife. It was really weird asking her for her weight.
 
I find that a 172/182 lands better with a slightly aft c.g. (i.e with someone in the back). Not only is it easier to flare, it floats a lot less too (more of a 172 issue than a 182 issue).
 
Ron Levy said:
I wouldn't count on that being true, and I definitely wouldn't count on them not skagging the tail due to overcontrolling on takeoff/landing.
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Yep...I once had a student land really hard on the tail with a guy observing in the back seat. It was a learning experience for all involved-especially for me...becoming complacent/too comfortable as an instructor will bite you in the ass...literally:D
 
It's more than just the gross weight increase, the plane indeed flies differently with the aft CG.

Margy's CFI always did at least one lesson with his students with the back seat loaded up to gross because, as suspected, most students won't be long until they fly that regime for real. I went along as human ballast on one of those flights when he was doing a Stage Check for another instructor...

Oh boy, I turned and hugged Margy good bye as the plane felt like it went 40 degrees nose up on takeoff as the student decided to demonstrate a departure stall 30 feet off the runway. This is when I heard what I characterize as the "CFI death scream" as the instructor is pushing as hard as he can against the student's control input (used only when the CFI is in imminent fear of death). I think the words were something like "If you drop this thing on its tail we're all gonna die."
 
Ryanb said:
I am a 70 hour PP and have not had someone ride backseat, yesterday i took a friend up and she asked if her friend could come to, i said because i haven't had enough time with pax in the backseat id rather not. I weigh 140 roughly and she weighs about the same and her friend about the same. How would the flying characteristics of the 172N 160hp change with a 140lb person in the backseat and 2 140lb people up front? Would the plane fly noticeably different like especially at critical phases of flight or about the same? Thanks
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With those weights, I don't think that you will notice much of a great difference. The first time that I took a back seat passenger was on my dual night XC so I had much less experience than you do now. I did have the security of my instructor being in the airplane, but I didn't notice much of a difference and this guy (someone my instructor knew) was probably around 180 or so with my instructor and I both being around 160. This was several months ago, so I don't remember what the fuel load was.

Every landing is different anyway and you always make adjustments by what you see and feel and while W&B isn't the same as wind conditions or air density, I doubt that 140 pound in the back seat of your 172 is going to feel very different for you in and of itself.
 
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I flew my 172k at full gross, or as heavy as I was willing, today. 37 gallons in the tanks, 370lbs up front, 190 in back with luggage. It was an eye opener on landing. I felt like we came down on the mains much harder than normal. Other than the landing everything else seemed near normal. Just a longer roll on takeoff and slower climb.
 
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