We have already noted above that, if we assume, as we do throughout this opinion, that the allegations in the complaint are true, petitioners suffered a taking of their private property as a result of MAC's activities. Because Minn.Const. art. 1, s 13, states that 'private property shall not be taken, destroyed or damaged for public use without just compensation therefor, first paid or secured,' we doubt that the legislature intended to cloak MAC with statutory provisions insulating it from claims for compensation required to be paid under that article. It seems obvious that it is 'necessary and convenient' that MAC have the power to take avigational easements in order to 'maintain and operate' the airport within the confines of our state constitution. We therefore hold that MAC does have the power to acquire avigational casements in this case. The extent, duration, terms, and conditions of those easements shall be determined by the trial court.

MAC also contends that petitioners' suit is barred by laches, by the existence of an adequate remedy at law, and by a balancing of the equities. Minnesota case law clearly indicates that mandamus is an equitable remedy and that equitable defenses are available. See, State ex rel. Hennepin County Welfare Bd. v. Fitzsimmons, 239 Minn. 407, 422, 58 N.W.2d 882, 891 (1953); Nationwide Corp. v. Northwestern Nat. Life Ins. Co., 251 Minn. 255, 265, 87 N.W.2d 671, 679 (1958).

MAC bases its argument that laches applies on the facts that the present airport has been in operation since the 1920's; it has been steadily expanded; and it has been obvious since 1945 that it was planned as the major airport for the metropolitan area.

A comprehensive historical analysis of MAC in the Minnesota Law Review points out that most of the major expansions to the present airport have taken place after 1950, with the largest part during the 1960's. Harper, The Minneapolis-St. Paul Metropolitan Airports Commission, 55 Minn.L.Rev. 363, 413. The article also points out that the major expansions were vigorously opposed by nearby residents. Thus, if laches is to be applied, should it only be applied for the time in which the operations of the airport have risen to a level that has had a detrimental effect upon the plaintiffs' properties, I.e., the late 1950's and 1960's? This issue was not directly passed upon by the court below. It appears, too, that there is not the complete factual setting that might be developed on this issue at a trial on the issue of inverse condemnation. We would prefer that the trial cort after a hearing make findings of fact and conclusions of law on this question. [FN 6]

[FN 6] Where the overflights and near-flights constitute a taking, the court below might wish to consider them as continuing torts. This court has indicated that the statute of limitations does not run from the initial trespass. Northern States Power Co. v. Franklin, 265 Minn. 391, 122 N.W.2d 26 (1963). We would think that MAC would prefer inverse condemnation to an injunction against further trespasses.

MAC finally asserts that an equitable balancing of the individual property owners' rights to compensation against the financial impact such payment would have on future aeronautical development is required as part of the mandamus action. Such a balancing, however, would be totally improper in an action which is basically one of eminent domain. The reason such a balancing is improper is that no individual seeks recovery in this action for personal injury, suffering, or inconvenience. Rather, petitioners seek compensation for a reduction in market value which amounts to a taking of property. This standard involves an inherent balancing, as was pointed out earlier in this opinion, in that the measure of recovery is based on decrease in value in the general marketplace rather than decrease in value to the individual property owner, thereby excluding recovery for the discomfort sustained by an unusually sensitive individual. This type of balancing exists when the state initiates the condemnation proceedings as well as when the injured property owner does so. But in either situation, a balancing of the individual's right to recover against that of MAC's utility to society is irrelevant.

MAC's final objection to the mandamus action is that no demand was made upon MAC to commence condemnation proceedings prior to this suit. That such a demand is necessary in this state before mandamus will issue to compel a public body to do an official act is well settled. See, State v. Adams, 260 Minn. 473, 110 N.W.2d 153 (1961); State ex rel. Sholes v. University of Minnesota, 236 Minn. 452, 54 N.W.2d 122 (1952); State v. Schaack, 28 Minn. 358, 10 N.W. 22 (1881); and State ex rel. Hull v. Davis, 17 Minn. 406 (429) (1871). Two exceptions have been carved out of this general rule. The first one is that no prior demand is necessary where a public duty rather than a private duty is involved. State ex rel. Currie v. Weld, 39 Minn. 426, 40 N.W. 561 (1888). The Weld case defined a public duty to be one which is specifically stated in the law itself and which does not result in a benefit or burden upon any particular person so that no particular person has the right to demand performance. This exception is inapplicable to an inverse condemnation action, such as is involved here, because specific property owners have the right to demand performance. The other exception from the general rule allows a suit without prior demand where such a demand would obviously be met by rejection and therefore would be useless. This exception was noted in Regan v. Babcock, 188 Minn. 192, 201, 247 N.W. 12, 16 (1933), wherein the court held that a prior demand was unnecessary because the state highway department's constructive participation in the fraudulent contracts plaintiffs sought to annul indicated that such a demand would have been rejected. The existence of this exception to the rule was again recognized in State ex rel. Sholes v. University of Minnesota, Supra, but was held inapplicable to the situation involved. That case involved an action to require the University's board of regents to adopt and enforce rules and regulations prohibiting all use of university property and facilities for the teaching or dissemination of any and all sectarian religious doctrine in any manner or form. This court held that in these circumstances a prior demand was necessary because numerous acts of questionable legality were involved which would require curtailing some activities and abolishing others. In essence, this court held that the actions requested were so varied and complicated, and required so much study and analysis, that a prior demand was necessary to give the University opportunity to act to rectify the situation before the court would intervene.

The case at hand is essentially different from State ex rel. Sholes v. University of Minnesota, Supra, in that the course of action petitioners seek to compel MAC to pursue is relatively elementary -- to institute condemnation proceedings against petitioners' properties. In addition, it would appear that a prior demand would have served no constructive purpose. A study of MAC's history shows that, on a number of occasions in the past, residents of the areas involved in this action have objected to airport expansions because of the increased possibility of danger as well as noise and air pollution. 55 Minn.L.Rev. 363, 414, Supra. These unsuccessful protests, coupled with MAC's initial denial of any liability and its vigorous defense of this action, indicate that a prior demand would have been summarily rejected and would not have served any useful purpose.

4. Is a class action the proper and most efficient method to adjudicate the rights of the parties affected? [FN 7]

[FN 7] Mr. Justice Yetka, Mr. Justice Scott, and the author of this opinion do not agree with this portion of it, which would deny the petitioners' request for a class action. We would permit the trial court to determine initially the members of the class, which would of necessity require a decision as to the perimeters of the avigational easement to be acquired. This determination would limit the number of litigants and the property involved. Thereafter the damages to be awarded, if any are, would be determined on an individual basis. We recognize that some of the owners of the parcels of land involved might not be entitled to damages but MAC should nonetheless acquire an avigational easement. This procedure would be much the same as in ordinary highway condemnation cases. In such cases property rights may be taken for highway purposes and yet in some acquisitions no damages are awarded -- i.e., slope easements which improve the landowners' property and cases in which special benefits exceed any damages. A class action here could parallel highway condemnation cases in which the property owners are all made parties in one action, but their awards of damages are thereafter determined separately. While Rule 23, Rules of Civil Procedure, provides that all members determined by the court to be eligible as such may elect not to be included, we would agree that to remain eligible each individual would have to give written notice of his intention to be a member of the class. For a discussion on class actions in suits against airports by property owners seeking inverse condemnation, see, Fadem and Berger, A Noisy Airport Is a Damned Nuisance, 3 Sw.U.L.Rev. 39, 65.

'Inverse condemnation as contemplated here appears to this Court to be incompatible with a class action since there are a multitude of individual issues and an absence of common issues. This Court cannot believe that the issues or the rights of the parties are common as between persons in close proximity to the airport, persons directly affected by overflights, persons whose property is not flown over but may be affected by noise, fumes, etc.'

[FN 8] The relevant portions of Rule 23, Rules of Civil Procedure, governing class actions are as follows:

Rule 23.01. 'One or more members of a class may sue or be sued as representative parties on behalf of all only if (1) the class is no numerous that joinder of all members is impracticable, (2) there are questions of law or fact common to the class, (3) the claims or defenses of the representative parties are typical of the claims or defenses of the class, and (4) the representative parties will fairly and adequately protect the interests of the class.'

Rule 23.02. 'An action may be maintained as a class action if the prerequisites of Rule 23.01 are satisfied, and in addition:

'(1) the prosecution of separate actions by or against individual members of the class would create a risk of (A) inconsistent or varying adjudications with respect to individual members of the class which would establish incompatible standards of conduct for the party opposing the class, or (B) adjudications with respect to individual members of the class which would as a practical matter be dispositive of the interests of the other members not parties to the adjudications or substantially impair or impede their ability to protect their interests; or

'(2) the party opposing the class has acted or refused to act on grounds generally applicable to the class, thereby making appropriate final injunctive relief or corresponding declaratory relief with respect to the class as a whole; or

'(3) the court finds that the questions of law or fact common to the members of the class predominate over any questions affecting only individual members, and that a class action is superior to other available methods for the fair and efficient adjudication of the controversy. The matters pertinent to the findings include: (A) the interest of members of the class in individually controlling the prosecution or defense of separate actions; (B) the extent and nature of any litigation concerning the controversy already commenced by or against members of the class; (C) the desirability or undersirability of concentrating the litigation of the claims in the particular forum; (D) the difficulties likely to be encountered in the management of a class action.'

Reversed and remanded for proceedings consistent with this decision.

SHERAN, C.J., not having been a member of this court at the time of the argument and submission, took no part in the consideration or decision of this case.