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#1
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Should I be scared -- C172 over Gross
Flown C172's for quite a while, and never had anybody in the back.
Now I'm planning on quite a trip, with 2 pax and luggage. When I fill the fuel to the *tabs*, calc everyone's weight honestly and consider baggage -- I'm 75 lbs over the 2450 gross on departure. Maybe 100 over gross if I assume a "lie about weight" factor or some inaccuracy with filling the tanks. Now I'm scratching my head about just how risky this is. I know (others) have pushed over gross in these planes way more under worse conditions, and have almost always gotten away with it. I'm inclined to just do it, and be cognizant that it will perform differently, i.e. don't expect the same picture on climbout that you would when solo. Risky? Or just roundoff error on the weight? Here are some other factors: This is the 160HP C172, standard. Departure runway is 5000'. No steep terrain to climb out of. Plenty of alternates along with the way with 3000 runways. Not particularly hot, humid, or high. 50 degrees at 1000 MSL for departure or any point of landing. I'm figuring I'm 3% over gross, causing most of my V speeds to increase 1.5%, so say -- instead of flying short final at 65 knots, I'd fly at 66 knots... OK wait I can't hold airspeed to +/- 1 knot on most days anyways. I'm thinking through many of the factors, and it is only a "little" over gross, only on the first hour or so of the trip. What else should I be aware of? Am I dangerous? T |
#2
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Should I be scared -- C172 over Gross
"tman" inv@lid wrote in message news I'm thinking through many of the factors, and it is only a "little" over gross, only on the first hour or so of the trip. What else should I be aware of? Am I dangerous? Like being a little pregnant. Ship the luggage. Vaughn |
#3
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Should I be scared -- C172 over Gross
tman wrote:
Flown C172's for quite a while, and never had anybody in the back. Now I'm planning on quite a trip, with 2 pax and luggage. When I fill the fuel to the *tabs*, calc everyone's weight honestly and consider baggage -- I'm 75 lbs over the 2450 gross on departure. Maybe 100 over gross if I assume a "lie about weight" factor or some inaccuracy with filling the tanks. Now I'm scratching my head about just how risky this is. I know (others) have pushed over gross in these planes way more under worse conditions, and have almost always gotten away with it. I'm inclined to just do it, and be cognizant that it will perform differently, i.e. don't expect the same picture on climbout that you would when solo. Risky? Or just roundoff error on the weight? Here are some other factors: This is the 160HP C172, standard. Departure runway is 5000'. No steep terrain to climb out of. Plenty of alternates along with the way with 3000 runways. Not particularly hot, humid, or high. 50 degrees at 1000 MSL for departure or any point of landing. I'd make this flight without hesitation. I would be considerably more reluctant in the heat of the summer but now? -- Mortimer Schnerd, RN mschnerdatcarolina.rr.com |
#4
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Should I be scared -- C172 over Gross
I would be much more concerned with the BALANCE part of W&B. Yes, 100
pounds over gross is not wise, at it reduces your safety margin with turbulence, and landing and takeoff distances. But you really need to make sure that your CG is not out of the allowable range -- with rear-seat pax and luggage, it could be pretty far back. Also, you have specific weight limits in the rear luggage area -- it's all in the POH. So, but your heaviest passenger in the front seat, and the lightest luggage in the rear area, and see where your CG lies. On Thu, 17 Apr 2008 05:53:07 -0400, tman inv@lid wrote: Flown C172's for quite a while, and never had anybody in the back. Now I'm planning on quite a trip, with 2 pax and luggage. When I fill the fuel to the *tabs*, calc everyone's weight honestly and consider baggage -- I'm 75 lbs over the 2450 gross on departure. Maybe 100 over gross if I assume a "lie about weight" factor or some inaccuracy with filling the tanks. Now I'm scratching my head about just how risky this is. I know (others) have pushed over gross in these planes way more under worse conditions, and have almost always gotten away with it. I'm inclined to just do it, and be cognizant that it will perform differently, i.e. don't expect the same picture on climbout that you would when solo. Risky? Or just roundoff error on the weight? Here are some other factors: This is the 160HP C172, standard. Departure runway is 5000'. No steep terrain to climb out of. Plenty of alternates along with the way with 3000 runways. Not particularly hot, humid, or high. 50 degrees at 1000 MSL for departure or any point of landing. I'm figuring I'm 3% over gross, causing most of my V speeds to increase 1.5%, so say -- instead of flying short final at 65 knots, I'd fly at 66 knots... OK wait I can't hold airspeed to +/- 1 knot on most days anyways. I'm thinking through many of the factors, and it is only a "little" over gross, only on the first hour or so of the trip. What else should I be aware of? Am I dangerous? T -- Jay (remove dashes for legal email address) |
#5
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Should I be scared -- C172 over Gross
"Jay Somerset" wrote in message ... I would be much more concerned with the BALANCE part of W&B. Yes, 100 pounds over gross is not wise, at it reduces your safety margin with turbulence, and landing and takeoff distances. But you really need to make sure that your CG is not out of the allowable range -- with rear-seat pax and luggage, it could be pretty far back. Also, you have specific weight limits in the rear luggage area -- it's all in the POH. So, but your heaviest passenger in the front seat, and the lightest luggage in the rear area, and see where your CG lies. Yawn!!!! |
#6
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Should I be scared -- C172 over Gross
On Apr 17, 9:53*pm, tman inv@lid wrote:
Flown C172's for quite a while, and never had anybody in the back. Now I'm planning on quite a trip, with 2 pax and luggage. When I fill the fuel to the *tabs*, calc everyone's weight honestly and consider baggage -- I'm 75 lbs over the 2450 gross on departure. *Maybe 100 over gross if I assume a "lie about weight" factor or some inaccuracy with filling the tanks. *Now I'm scratching my head about just how risky this is. *I know (others) have pushed over gross in these planes way more under worse conditions, and have almost always gotten away with it. *I'm inclined to just do it, and be cognizant that it will perform differently, i.e. don't expect the same picture on climbout that you would when solo. Risky? *Or just roundoff error on the weight? *Here are some other factors: This is the 160HP C172, standard. Departure runway is 5000'. No steep terrain to climb out of. Plenty of alternates along with the way with 3000 runways. Not particularly hot, humid, or high. *50 degrees at 1000 MSL for departure or any point of landing. I'm figuring I'm 3% over gross, causing most of my V speeds to increase 1.5%, so say -- instead of flying short final at 65 knots, I'd fly at 66 knots... OK wait I can't hold airspeed to +/- 1 knot on most days anyways. I'm thinking through many of the factors, and it is only a "little" over gross, only on the first hour or so of the trip. *What else should I be aware of? *Am I dangerous? Not really. The slight excess is fuel which will be burnt off. before landing time. Remember the structure is stressed to much higher G than 1.015 and if you just slapped a bigger engine in the MTOW would be increased to as much as 2500. What is dangerous is the position of the COG and the reduced climb. Make sure you do a weight and COG calc. for the trip. I can tell you that you should probably expect a more tail heavy feel than you are used to which will promote a tendency to rotate too early. Just raise your Vx by 5k and she'll be fine. Your climb will be reduced to (say) about 400 fpm at 2000' (if I remember correctly). Don't crash it or you will be in real trouble :-0 Cheers |
#7
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Should I be scared -- C172 over Gross
WingFlaps wrote:
Not really. The slight excess is fuel which will be burnt off. before landing time. Remember the structure is stressed to much higher G than 1.015 and if you just slapped a bigger engine in the MTOW would be increased to as much as 2500. What is dangerous is the position of the COG and the reduced climb. Make sure you do a weight and COG calc. for the trip. I can tell you that you should probably expect a more tail heavy feel than you are used to which will promote a tendency to rotate too early. Just raise your Vx by 5k and she'll be fine. Your climb will be reduced to (say) about 400 fpm at 2000' (if I remember correctly). Don't crash it or you will be in real trouble :-0 Actually, your tongue-in-cheek comment raises a good point. Operating over gross may well void your insurance. So, question to the OP: do you really want to make a flight with no insurance in force? Even a small mishap that gets investigated may well result in your insurance company abandoning you when you need them most. I'd read my policy carefully before making this flight just to be sure. Matt |
#8
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Should I be scared -- C172 over Gross
On Apr 17, 5:53*am, tman inv@lid wrote:
I'm thinking through many of the factors, and it is only a "little" over gross, only on the first hour or so of the trip. *What else should I be aware of? Many things. That's inherently the problem with operating outside the certified limits. The certification limits provide you with certain protections. By operating outside those limits, you give up some protection. What do you give up? Well, that depends on what set the limit. Now there are two basic ways to approach this. First, you can approach it the engineer way. That's how (modern) test pilots approach this sort of problem. They operate outside the defined limits all the time (it's in the job description) and most of them are trained engineers anyway. They figure out what they are doing, what they can expect out of the operation, decide whether the risk is acceptable, plan for it, and fly the plan. So how do you do this? Start with the basics. What is the maximum available gross weight for that make and model? Are there STC's that increase it? What sort of gross weight limits are handed out on ferry permits? Consider the effect on cg. The cg envelope generally narrows with increasing weight. Consider performance - what will climb be like? Cruise? How about go- around with flaps? Perhaps you need to limit flaps on landing (in case they don't retract)? What about the g-loading? Normal category is 3.8, now you may have less (or not - is that what limits gross weight on that plane?) - how much turbulence can you expect? Don't forget that for older planes, the W&B is mostly a work of fiction anyway. The only real W&B is the kind you do with scales. Most of them are done by subtracting the weight of equipment removed (generally overestimated, because the cabling for avionics is mostly left in) and adding weight installed (often underestimating because fabbed cables and such are not included) and ignoring the (significant) accumulation of dirt and grease. Ultimately, what you are doing is substituting your judgment for regulation. This has a lot in common with deciding that while the speed limit is 55 here, in your judgment 60 is safe enough, even with passengers in the car. If that's not something you would do, you probably should not do this either. Or there's another way. Hey, people do this all the time, seems to work out OK, why not give it a shot? That's a lot how test pilots used to operate way back when. A lot of them died that way, too. *Am I dangerous? Of course you're dangerous. You're considering transporting your passengers by light airplane rather than a car. That's demonstrably more dangerous. The question is whether the risk is reasonable for you and them. Now I happen to know (having faced almost this situation and done the above analysis) that the margins are acceptable for me - and were acceptable even when I had something like 100 hours. But who the hell am I? Maybe I have graduate degrees in engineering, an ATP, and an A&P - not to mention several kinds of CFI. Then again, maybe I'm just a guy who plays flight sim a lot. Only the people who have met me and flown with me know for sure. If you're going to operate outside the rules, you really should know what safety margins, if any, you are giving up - and that means doing your own analysis. Michael |
#9
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Should I be scared -- C172 over Gross
On Apr 17, 2:53*am, tman inv@lid wrote:
Flown C172's for quite a while, and never had anybody in the back. Now I'm planning on quite a trip, with 2 pax and luggage. The biggest problem with flying a little overgross is the same problem with flying at high density altitude. The plane will perform different and a pilot who isn't expecting this can run into serious problems. The site picture over the nose will look a bit different. This is why I always teach my students to climb out on airspeed. I know some CFIs focus on the site pitch picture but that only works with consistant weight, altitude, etc. Many pilots have bitten the big one because they keep pulling the nose up when climbing out of mountain airports until they stall it. They keep trying to achieve the site picture their CFI taught them down in the valley. -robert, CFII |
#10
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Should I be scared -- C172 over Gross
"Robert M. Gary" wrote in message
... On Apr 17, 2:53 am, tman inv@lid wrote: Flown C172's for quite a while, and never had anybody in the back. Now I'm planning on quite a trip, with 2 pax and luggage. The biggest problem with flying a little overgross is the same problem with flying at high density altitude. The plane will perform different and a pilot who isn't expecting this can run into serious problems. The site picture over the nose will look a bit different. This is why I always teach my students to climb out on airspeed. I know some CFIs focus on the site pitch picture but that only works with consistant weight, altitude, etc. Many pilots have bitten the big one because they keep pulling the nose up when climbing out of mountain airports until they stall it. They keep trying to achieve the site picture their CFI taught them down in the valley. -robert, CFII Agree Agree!!!! |
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