The information given to Mark1234 sounds the same as that I have heard, the 152 has a lesser flap limit due to less than adequate climb performance at gross weight with 40 degrees of flap. The 152 seems to have a propeller optimized more for cruise than climb. I have taken off 152's from runways where they struggled out where a 150 in the same runway had no difficulty, in otherwise very similar operating conditions. I have not done a detailed comparison of performance data though.
The airspeed required to obtain a climb in a 150 with full flaps will be very close to stall warning speed.
"Safe" is a very challenging thing to measure. Hence my pasting in the wording of the standard which would be applied to the 150, both back then, and now. The current standard's wording for the same requirement is:
523.77 Balked Landing
(a) [Each normal, utility, and aerobatic category reciprocating engine-powered aeroplane of 6,000 pounds or less maximum weight must be able to maintain a steady gradient of climb at sea level of at least 3.3 percent with:
(1) [Takeoff power on each engine;
(2) [The landing gear extended;
(3) [ The wing flaps in the landing position, except that if the flaps may safely be retracted in two seconds or less without loss of altitude and without sudden changes of angle of attack, they may be retracted; and
[(4) A climb speed equal to VREF, as defined in 523.73(a).
Vref would be about 1.3 times stalling speed in that configuration. Still pretty slow. The reference to skill still applies by a reference from a preceding paragraph. Thus the reference to airspeed for climb is the only difference between the two standards.
The earlier (previous post's) standard (CAR3) is the wording which would apply to the designs of both the 150 and the 152, though at the time that the 152 design was being validated by Cessna the newer wording would have been available (and for certain Cessna would know it well) so Cessna would have have compliance with the newer standard in their mind too.
The challenge is deciding what "without requiring.... exceptional skill on the part of the pilot" really means. That is where we are measuring "safe" as objectively as possible. The later standard does add one more condition, which reduces the demonstration pilot's opportunity to use his/her exceptional skill so as to show "safe" compliance of the aircraft. It is understood that the demonstration pilot's recent experience performing such flying, might give that pilot exceptional skills in that aircraft type. This is to be discounted by the pilot who performs the certification evaluation flying.
So how sloppy is that pilot to be to be fair to both sides? I know that I'm doing it very fairly when I pilot an aircraft type which I've never flown before, and show compliance with a requirement. If I've never flown that type before, I'm certain that I do not have exceptional skill in it. When Flying Cessnas, I have to be more cautious, as I've flown many types before. I try to be a tiny bit careless, and see if the plane bites me. If it's a trainer type, more careless.
During a Transport Canada approved flight test for the purpose of confirming the proper repair of a flying club 172, I purposefully took off with full flaps (only 30 in that model). I did re-land it before I left the runway. The instructor who accompanied me (for insurance reasons) was apparently very surprised this was possible at all. Later in that flight he asked me to demonstrate a roll to him. I would not. I later learned that he was the club safety officer, and second most "experienced" instructor. This was a larger club with more than 25 aircraft. I was reminded that instructors don't know everything.
During a recent flight test in a multi engine aircraft with external modifications, I simply could not make it climb as required (one only one engine) by the prevailing standard. I tried for more than 30 minutes. It did not pass the flight test.
So I return to my previous statement: Up high, in a safe environment, put the plane into slow flight, apply full power, and see if you can make it climb. If you cannot, question the airworthiness of the aircraft. It sounds like Lost Pilot Standing is already questioning the airworthiness of aircraft he flies, with terms such as "condition", "battered" and "abused". I assure you that these terms would not apply at all to the "typical" Canadian Cessna 150 I have seen and flown. Honestly, if the aircraft is not "airworthy" as measured by the standards of maintenance of the airframe, engine, and propeller manufacturer's respective publications, it might not perform as required by the design standards. This is one of the many very good reasons to assure that the aircraft you fly has been correctly maintained.
I would agree that a flying instructor who owns the flying school, and the Cessna 150 they are flying would generally be extended credit as a compotent pilot. As a compotent pilot, I presume that they are flying an aircraft which they have found to be airworthy. That said, with level terrain, I would wonder why that pilot could not accomplish something which the design standard says must be possible (and I have done). I am not in a position to speculate. Aircraft stick flaps, I would hope that intructors are training students what to do when it happens, so as to make the best use of the aircraft capabiltiy demonstrated during certification, which was required for exactly that circumstance.
"Safe", airborne in a battered and abused aircraft? Perhaps not so much...
Pilot DAR