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  1. #1
    SSDriver Guest

    C172M - landing finesse with passengers?

    Hi,
    Was looking for feedback on what differences you might make assuming you had 3 passengers with you. Using the 2300 lb figure. I know what the POH says but I'm curious on real world experience. Do you prefer to carry more speed on final? Max flaps? we generally train with 20degrees with 2 souls and I use 65 over the threshold.

    I flew with my CFI and a FAA observer in the back seat. Nothing happened but I noted my landings were ALOT firmer and it was bumming me out. Soon I'll have the opportunity to fly my wife and children and I want to make sure this is sorted in my head before I take that responsibility on.


    Thanks for any advice!
    Drew

  2. #2
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    Vs0 * 1.3

    Remember that the Vs0 and Vs1 speeds in the book are given for gross weight, so we typically fly the approach a little fast anyway, because we usually aren't at gross when training in a 172. The only time I land a 172 with less than 30 degrees of flap is if there is a gusty wind, and then I add no more than half the gust factor to my speed. Trim for the final approach speed! I want to put no pressure on the yoke until I level off just above the runway and hold it off until the main wheels touch.

    My point, overall, is not to overthink it. I am used to flying solo or with one passenger/instructor in the front seat, but recently I got to take an aunt and uncle for a ride in a Cherokee. I didn't even think about the effect on CG from having someone in the back seat. I just flew the plane the same as usual, got down low, held it off, and touched down very gently. I can also sense the difference in flying the Citabria without an instructor in the back seat, but again, I don't fly it any differently.

    Jared

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    I would say that your "problem" is that you're flying your approaches too fast when you're light. 65 knots = 1.3 Vso only when the airplane is at gross weight. Assume that your normal flights have been with only 2 aboard and less than full tanks, you're probably flying a good 5 knots fast. So first practice a few landings with a lower approach speed at your typical weights.

    But it's also true that with the back seats full, although you aren't over gross, the CG will be farther back. That means that the aircraft will be easier to pitch up, and if you've not experienced it before in training, it can surprise you. It also means that stall recovery may require a more definitive push on the yoke, as opposed to simply relaxing the back pressure. That's why I think it's a good idea to go up with your instructor with the airplane loaded at full aft CG, to get a feel for the difference in the way the airplane flies, before you do it by yourself as a private pilot.

    As to your specific questions, I see no reason to change your use of flaps from light to heavy weights or from forward to aft CG, except for this: If you have to go around with a full load and aft CG and you're carrying full flaps, you will have a greater need to retrim and a harder push on the yoke, to keep the nose down to avoid a trim stall. It's not overwhelming, but it is very definitely noticeable.

    And definitely do not use a faster approach speed, except regarding gusty winds. That rule doesn't change. A faster approach speed only makes your job more difficult.

    Cary

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    You must have small passengers. I get to 2300 lb with two passengers (one of whom is a kid), not three.

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    I get to 2300 lb with two passengers (one of whom is a kid), not three.
    Carry less fuel.

    Cary

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    That only goes so far. I can get 180 lb extra that way if I push it all the way to my reserve limit. That will make for a lot of fuel stops. A 172 only holds 40 gallons usable. I can get 8.5 GPH at altitude, but in the pattern, it's more like 11.

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    Quote Originally Posted by MAKG View Post
    That only goes so far.
    Literally.

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    I can get 8.5 GPH at altitude, but in the pattern, it's more like 11.
    Not really. On take off, a 160 hp 172 will burn about 10, but once you level off in cruise, you're down to 8.5, but on downwind in the pattern it'll be more like 7.5, and in descent, it's down around 5.5. So overall, you'll burn much less doing pattern work than in cruise. If you're staying relatively close to the airport just sight seeing, there's no really good reason to carry much more than a decent reserve, which to my way of thinking equates to 45 minutes vs. the FAA's requirement of 30 minutes. For longer flights, especially in iffy weather, I prefer a larger reserve and usually land with an hour or so left.

    In my airplane, I have a very sophisticated fuel flow gauge. With 180 hp, it will approach 12 on take off from a near sea level airport, although a little less at our elevations here. At cruise, it's very consistent at 9.8. Typically if I stay in the pattern, I'll actually use less than 8. Since I rarely have full tanks except right after filling up, I stick my tanks before every flight, and the stick and the fuel flow gauge are very close. That really helps me to determine how many "real people" I can carry.

    So if you're going up for a local sight-seeing flight, I would think that carrying roughly 1 1/2 hours of fuel (12 gallons) would do the trick, adding 170 lbs to your passenger carrying capacity. Throttle back a bit as you flit around, get 8 gph, and you should be able to carry 4 reasonably size adults, a couple of guys at 180 each and a couple of gals at 140 each, for a nice 45 minute flight. That's assuming that the 172 you rent has the typical 880 lb. useful load, subtracting 75 lbs for 12 gallons of gas, leaving 800 lbs for people and stuff.

    Of course, if you're going some distance and plan to be in the air for 3 hours at a stretch, that's different. Now you need about 175 lbs. of fuel, reducing your capacity to about 700 lbs. for people and stuff. You can still carry the same people, just not as much stuff, and if you ramp up the throttle a bit more, you have to cut the stuff down more.

    Of course, maybe the airplane you're renting weighs a lot more empty than typical, and you have to account for that. But I should think you can carry more than just you, another adult, and a kid and still have pretty decent range and reserves.

    Cary

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    Others have already pointed out one of my pet peeves- 1.3xVso=1.3xVso. It is counterproductive to fly an approach faster than this barring gusty conditions, in which case you should add 1/2 the gust spread.
    Landing is energy management where the pilot is initially getting rid of potential energy (altitude), while getting to a specific point on the runway. While doing this one must minimize kinetic energy (speed), because once you get to that specific point on the runway it is time to get rid of kinetic energy. The more kinetic energy you carry on approach the more runway you need to get rid of it.
    A common practice among pilots flying fast approaches is to attempt to force the airplane onto the runway when it still has excess kinetic energy. Don't try to land the airplane,cry to keep it from landing at this point. When it runs out of excess energy and stalls it will land itself.

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    "Forcing" a 172 onto the runway is a good way to get a nosegear replacement....

    The 180 HP I like to rent once had a porpoised landing severe enough to shear off the nosegear pin. It took several tries to get that fixed; the nosegear strut kept going flat. The entire cylinder was eventually replaced, and now it works a lot better.

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    The nose struts need servicing just about every annual, anyway. So far I've only made it through one annual in 8 years in which the seals didn't need replacing, this last one, but it's down a bit now, so maybe it should have been done anyway. As long as it doesn't go flat between flights, it's not an issue, but too often is a pain in the neck.

    Cary

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    It went flat every other week. It sucked bad. It's much better now that the cylinder has been replaced.

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    Yeah, that's a bit extreme.

    Going back a bit, the damage that can occur when forcing an airplane onto the runway too fast, leading to porpoising, can range from little to extreme. In "olden times", a minor propeller strike, such as is common with Mooneys that porpoise, resulted in repairing the prop, but now it requires a complete engine tear-down at a cost that usually exceeds 75% of a complete overhaul. Most SE Cessnas can incur firewall and fuselage damage, especially older 182s (pre-1970), which have notoriously weak firewalls, because the nose gear is directly attached to the firewall. In addition to porpoising, though, the wheel-barrowing effect of forcing the nose down can result in a total loss of control and departing the runway.

    All this, because touch down speeds are excessive--which typically results from excessive approach speeds. If that's not a sufficient incentive to get speed under control, I don't know what is.

    Cary

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    Quote Originally Posted by UHBlackhawk View Post
    Others have already pointed out one of my pet peeves- 1.3xVso=1.3xVso. It is counterproductive to fly an approach faster than this barring gusty conditions, in which case you should add 1/2 the gust spread.
    Landing is energy management where the pilot is initially getting rid of potential energy (altitude), while getting to a specific point on the runway. While doing this one must minimize kinetic energy (speed), because once you get to that specific point on the runway it is time to get rid of kinetic energy. The more kinetic energy you carry on approach the more runway you need to get rid of it.
    A common practice among pilots flying fast approaches is to attempt to force the airplane onto the runway when it still has excess kinetic energy. Don't try to land the airplane,cry to keep it from landing at this point. When it runs out of excess energy and stalls it will land itself.
    I agree...airspeed is key, no matter how many passengers you have. No one should change their methods based on payload.

    Bob Gardner

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    Quote Originally Posted by bobmrg View Post
    I agree...airspeed is key, no matter how many passengers you have. No one should change their methods based on payload.

    Bob Gardner
    Yeah, but Vs0 is a function of payload. UHBlackhawk's advice is still germaine -- the POH Vs0 is for max gross weight, so you should fly slower with a light load, rather than faster with a heavy load.


 

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