C208 question, wheels
Thread Starter
Join Date: Jun 2010
Location: TinselTown
Age: 45
Posts: 203
Likes: 0
Received 0 Likes
on
0 Posts
C208 question, wheels
Why in designing the 208 did the engineers at Cessna decide to sweep the main gear slightly forward? I get perhaps they had to be at that fuselage frame for structural purposes, even then they may have wanted to sit on their arse - but why exacerbate the situation?! Over 30 years of pogo sticks, bent rear bulkheads, boofed in tailcones, red faced pilots - what was the overriding design consideration that made all this necessary?
Imagine if any of the other 200 series were designed the same way. Ridic
Imagine if any of the other 200 series were designed the same way. Ridic
Thread Starter
Join Date: Jun 2010
Location: TinselTown
Age: 45
Posts: 203
Likes: 0
Received 0 Likes
on
0 Posts
structural stress reduction on the fuselage undercarriage box sections
C of G envelope advantages
If the wheels were further aft, at forward CofG locations the down load on the tail to rotate at takeoff is higher. This would potentially lead to longer takeoff runs until there was sufficient elevator authority to raise the nose.
Errr... aren't most Cessna main gears swept forward? 
Indeed, a quick check on Google images for Cessna 152, 172, 182, 206, 207, 208 & 210 all seem to show main gear that sweep forward.
Indeed, a quick check on Google images for Cessna 152, 172, 182, 206, 207, 208 & 210 all seem to show main gear that sweep forward.
Join Date: Apr 2008
Location: Australia
Posts: 490
Likes: 0
Received 0 Likes
on
0 Posts
The relationship between the main gear, the CG and the centre of lift is important for a smooth transfer of weight between wheels and wings at takeoff and landing.
If the main wheels are too far behind the centre of lift the aircraft will tend to over rotate on takeoff and thump the nosewheel down on landing. The change in arms between the tail, the CG and where the weight is being supported (wings or wheels) results in a change in elevator input required as the AOA changes.
So the gear geometry is mainly dictated by how you want the aircraft to respond as you raise or lower the nose on the runway. A tendency to sit on it's tail is more due to a longer fuselage allowing you to load significant weight behind the main gear - a problem that isn't always confined to small aircraft.
If the main wheels are too far behind the centre of lift the aircraft will tend to over rotate on takeoff and thump the nosewheel down on landing. The change in arms between the tail, the CG and where the weight is being supported (wings or wheels) results in a change in elevator input required as the AOA changes.
So the gear geometry is mainly dictated by how you want the aircraft to respond as you raise or lower the nose on the runway. A tendency to sit on it's tail is more due to a longer fuselage allowing you to load significant weight behind the main gear - a problem that isn't always confined to small aircraft.
Folks,
An old Aeronautical Engineer friend, who has written more than a few repair schemes for sundry Cessna, has always likened the design common to all fixed gear Cessna main gear as a bit like having two can openers trying to open up the spam can.
Tootle
An old Aeronautical Engineer friend, who has written more than a few repair schemes for sundry Cessna, has always likened the design common to all fixed gear Cessna main gear as a bit like having two can openers trying to open up the spam can.
Tootle
Thread Starter
Join Date: Jun 2010
Location: TinselTown
Age: 45
Posts: 203
Likes: 0
Received 0 Likes
on
0 Posts
great for the photo montage RHS! yes they are but you don't need a pogo stick for them to stop them falling on their bums.
thanks andrewc that must be it. Still.. would have thought they could engineer that out, bigger elevator or something.
thanks andrewc that must be it. Still.. would have thought they could engineer that out, bigger elevator or something.
ATR72's also have a wee tail stand.
But then again... they're french/italian!
Seriously tho, I suspect it probably has more to do with being loaded via rear stairs (ie. way aft of the CoG). In the 208B's case, because of the lengthened fuselage (ie. even more aft of CoG), and rear stairs, it isn't impossible to add a couple of hundred kilos to the very rear of the aircraft as pax start boarding, especially if the first couple decide to sit on the back bench.
My very first flight with pax, I forgot to put the tail stand in as I got distracted by the military guy with the big gun asking for my security clearance (which I'm fairly sure I didn't have) after we arrived.
We then loaded up the 10 pax (who weren't exactly what one would claim were "standard passenger weights"). I closed the door, turned around to take the tail stand out and was like
Got lucky and have NEVER forgot the tail stand ever since. Even with guys with guns asking questions after getting out.
But then again... they're french/italian!
Seriously tho, I suspect it probably has more to do with being loaded via rear stairs (ie. way aft of the CoG). In the 208B's case, because of the lengthened fuselage (ie. even more aft of CoG), and rear stairs, it isn't impossible to add a couple of hundred kilos to the very rear of the aircraft as pax start boarding, especially if the first couple decide to sit on the back bench.
My very first flight with pax, I forgot to put the tail stand in as I got distracted by the military guy with the big gun asking for my security clearance (which I'm fairly sure I didn't have
) after we arrived.We then loaded up the 10 pax (who weren't exactly what one would claim were "standard passenger weights"). I closed the door, turned around to take the tail stand out and was like
Got lucky and have NEVER forgot the tail stand ever since. Even with guys with guns asking questions after getting out.
Saw a jabbapoo one day that kept sitting on its arse every time someone got in the back seats. Turned out the main gear was put on backwards. And not by the owner...
