To return to the original issues being a Robin DR 400 owner and having flown many of the type I have noticed some conflicting data in the performance data that seem to conflict with the rules of physics, for example the early -180 aircraft fitted with a -68” propellor has the same take off performance as later aircraft fitted with -64” propellor yet the greater pitch of the -68” propellor gives ( not surprisingly) greater cruise performance.
There are a large number of fixed pitch propellors approved for the DR400, the -180 has five approved in the type data sheet and my concern with DR400 performance based accidents is that the wrong performance data is used because the aircraft paperwork does not reflect the type of propellor fitted. I know in a club environment the flight manuals get lost so these are usually locked away and copies made available to The club members. These are uncontrolled copies and may not reflect changes made to individual aircraft.
I’ve been wondering about that @A_and_C.
Have not been exposed to Robins a lot but at one time was looking to buy a HR100 for it’s stellar range. When I looked at the POH, it was stunned. Very few performance data, some even handwritten with a stamp of the factory saying it was them who wrote it, e.t.c. I was fully prepared to fly a full performance evaluation to feed my flight planning had I bought this airplane.
Also seeing that there are seemingly countless versions of engines, props, e.t.c for the same airplane type, as you say confusion and mistakes might well be happening. I wonder if at times they simply built airplanes and then saw what motors they had left on the shelf and zoom, there was a new version? Tongue in the cheek, but somehow that is how it looks.
Of course that also applies to others, PA28, C172 and more, which have various engine/prop combinations. But somehow I felt it is a little bit less messy.
(talking of French designs, I vaguely recall a movie(?) of a flying Curé on a Velosolex which was driven by Absynthe…. never could find it back, but maybe it rings a bell with one of our friends from France here. It looked really funny, a bit along the lines of the nun and her 2CV in the DeFunes movies. )
EuroFlyer wrote:
It may be an unpopular view….. and I know there are some so called four seaters which in fact are only 1-2 seaters like the 150 but they’re being used for training – that’s a different game.
I fully agree with you. Modern certification standards should consider that all aircraft must be able to be depart with all seats occupied with adults of average weight. Of course, average weight was less when most GA models were certified, but it still didn’t work out even then.
Cars have become much heavier and in turn much sturdier, safer and more capable over the last four decades. The same should have happened with aircraft, heavier, crashworthier, greater wingspan, more powerful engines and all at the same price as before. But it didn’t, because GA is a dysfunctional sector of the economy.
They can but not with full tanks, on a hot day, etc.
This tradeoff is widely accepted. The problem is wishful thinking 
@airborne_again
Yes, thanks for the correction. I mixed introductory flights with fi with flights to promote aerial sports.
MedEwok wrote:
Modern certification standards should consider that all aircraft must be able to be depart with all seats occupied with adults of average weight.
and full fuel or at least fuel for a certain amount of time like 2 hours minimum.
MedEwok wrote:Cars have become much heavier and in turn much sturdier, safer and more capable over the last four decades. The same should have happened with aircraft, heavier, crashworthier, greater wingspan, more powerful engines and all at the same price as before. But it didn’t, because GA is a dysfunctional sector of the economy.
Primarily it did not happen because of the impossible cost of certification. No company in recent years has managed to certify a clean sheet design without either bancruptcy or cash injection / change of ownership in the process. Add to it cost of liability insurance. Add to that quasi Monopoly with avionics and engine makers. All that brings totally irrational prices to airplanes which should cost a maximum of 100k but cost a million. Yes, I suppose one can call that dysfunctional.
The most important factor in light aircraft design is minimizing weight, planes are not cars and induced drag (drag that is a direct result of lifting weight) is high in relation to the rolling resistance of a car, when carrying the same weight. For that reason cars can by comparison carry a lot of weight, including their own fat, inefficient structures and equipment, without paying the same huge penalty in power consumption. Trains take it a step further, which is why heavy freight can be carried least expensively by rail.
I just finished spending four million dollars of somebody else’s money developing a small piece of aircraft equipment that increases power density of the component by about a factor of two. The application is a fairly light aircraft so it was worth the investment to lose half the weight previously associated with the required power level, along with increasing reliability. Every bit of weight saved means a little more fuel on board.
If you want to carry high payloads in a sturdy crash proof airframe there is no lack of options, a Piper Aztec comes to mind, carry who and whatever you like and pay the fuel bill for 500 HP, which regardless of the engine type in use will be high. A former boss had one years ago, his wife loved its steel tube fuselage and imposing bulk and they flew it regularly. Like everybody else he very rarely flew it with more than 2 on board.
Mooney_Driver wrote:
No company in recent years has managed to certify a clean sheet design without either bancruptcy or cash injection / change of ownership in the process.
What about Elixir?
Diamond advertises with a safety cell kind of structure for crash protection. What about Cirrus?
The Cirrus has energy absorbing structure under the seats, it is prohibited to fit anything into the void under the seats to allow the seat to collapse into the void in a controlled way.
