PDA

View Full Version : Definition


evilroy
7th Apr 2010, 05:14
We have an aircraft certified under FAR Part 27. The flight manual gives a figure for the "maximum gross weight". No figure for MTOW is given.

What is the definition for "maximum gross weight"?

Can I use it as MTOW? Is it the weight the aircraft is never to exceed?

The flight manual does not give a definition, and I can't find a definition in the FARs. Have found lots of opinions around the place but nothing authorative.

TIA.

zonnair
8th Apr 2010, 08:57
Hey evilroy,

Quotation from ASA Dictionary or Aeronautical Terms:
"Gross weight (aircraft specification). The loaded weight of an aircraft. Gross weight includes the total weight of the aircraft, the weight of the full and oil, and the weight of all the load carrying."

To me the Max gross weight means, in that case, the maximum weight for the phase of flight. In other words, For take off your maximum gross weight allowed is equal to your MTOW, but for Landing your maximum gross weight will be less.

Sorry if it is not complete. Anyone anything to add?

ZNA

enicalyth
8th Apr 2010, 09:36
Assuming that we differentiate between taxi weight and take-off weight as a given. There is presumably a mother of all weights that can never be exceeded for take-off, regardless. And then there will be a maximum permissible dependent on the actual conditions. Whichever set of regulations is in force there would surely have to be a recognition that maximum permissible and all-out maximum are likely to differ and the former can never exceed the latter?

massman
8th Apr 2010, 10:51
Have you tried the manufacturer ?

bigduke6
9th Apr 2010, 20:41
from faa.gov online FARs

Title 14: Aeronautics and Space
PART 27—AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT
Subpart B—Flight
General
§ 27.25 Weight limits.

(a) Maximum weight. The maximum weight (the highest weight at which compliance with each applicable requirement of this part is shown) must be established so that it is—
(1) Not more than—
(i) The highest weight selected by the applicant;
(ii) The design maximum weight (the highest weight at which compliance with each applicable structural loading condition of this part is shown);
(iii) The highest weight at which compliance with each applicable flight requirement of this part is shown; or
(iv) The highest weight in which the provisions of §§27.87 or 27.143(c)(1), or combinations thereof, are demonstrated if the weights and operating conditions (altitude and temperature) prescribed by those requirements cannot be met; and
(2) Not less than the sum of—
(i) The empty weight determined under §27.29; and
(ii) The weight of usable fuel appropriate to the intended operation with full payload;
(iii) The weight of full oil capacity; and
(iv) For each seat, an occupant weight of 170 pounds or any lower weight for which certification is requested.
(b) Minimum weight. The minimum weight (the lowest weight at which compliance with each applicable requirement of this part is shown) must be established so that it is—
(1) Not more than the sum of—
(i) The empty weight determined under §27.29; and
(ii) The weight of the minimum crew necessary to operate the rotorcraft, assuming for each crewmember a weight no more than 170 pounds, or any lower weight selected by the applicant or included in the loading instructions; and
(2) Not less than—
(i) The lowest weight selected by the applicant;
(ii) The design minimum weight (the lowest weight at which compliance with each applicable structural loading condition of this part is shown); or
(iii) The lowest weight at which compliance with each applicable flight requirement of this part is shown.
(c) Total weight with jettisonable external load. A total weight for the rotorcraft with a jettisonable external load attached that is greater than the maximum weight established under paragraph (a) of this section may be established for any rotorcraft-load combination if—
(1) The rotorcraft-load combination does not include human external cargo,
(2) Structural component approval for external load operations under either §27.865 or under equivalent operational standards is obtained,
(3) The portion of the total weight that is greater than the maximum weight established under paragraph (a) of this section is made up only of the weight of all or part of the jettisonable external load,
(4) Structural components of the rotorcraft are shown to comply with the applicable structural requirements of this part under the increased loads and stresses caused by the weight increase over that established under paragraph (a) of this section, and
(5) Operation of the rotorcraft at a total weight greater than the maximum certificated weight established under paragraph (a) of this section is limited by appropriate operating limitations under §27.865(a) and (d) of this part.

Old Smokey
17th Apr 2010, 04:40
Maximum Gross Weight is a STRUCTURAL limit.

Maximum Takeoff Weight (MTOW) is a PERFORMANCE limit.

When the performance capability of the aircraft for Takeoff (or Landing after considering Burn off) exceeds the Structural limit, then the Structural limit becomes the MTOW. (Similar considerations arise when the Structural / Performance limited gross weight of the aircraft exceeds the pavement limit).

Regards,

Old Smokey